Renal diseases and blood pressure dysregulation in acute care: Pathophysiology, clinical patterns

Abstract

Blood pressure (BP) abnormalities are clues to make differential diagnosis and prognostic indicators in various renal diseases in the emergency department (ED), arising from and contributing to kidney dysfunction via activation of the renin-angiotensin-aldosterone system, impaired perfusion, volume overload in chronic kidney disease (CKD) patients, inflammatory processes, and traumatic structural injury. This narrative review summarizes BP patterns and pathophysiology across common renal conditions in the ED, including acute kidney injury, CKD, end-stage renal disease, glomerulonephritis, renal trauma, pyelonephritis, renal artery stenosis, nephrolithiasis, renal infarction, and renal tubular acidosis. Distinct BP profiles are observed: Hypotension often indicates prerenal, septic, or shock-associated acute kidney injury, severe infection, trauma, or shock, while hypertension predominates in CKD, end-stage renal disease, and ischemic or obstructive conditions due to renin-angiotensin-aldosterone system activation and sodium retention. Some disorders show variable BP patterns depending on stages, severity, and comorbidities. Overall, BP abnormalities provide valuable diagnostic and management guidance. Recognizing these predictable hemodynamic responses supports timely diagnosis, risk stratification, and targeted ED management.

Key Words: Acute kidney injury; Chronic kidney disease; Glomerulonephritis; Renal artery stenosis; Renal infarction; Blood pressure; Hypertension; Hypotension; Emergency medicine

Core Tip: Blood pressure abnormalities in renal diseases present distinct yet mechanistically predictable patterns in the emergency department. Hypotension often reflects hypoperfusion, sepsis, or trauma, while hypertension is commonly driven by renin-angiotensin-aldosterone system activation, volume overload, or renal ischemia. Recognizing these characteristic hemodynamic profiles enables rapid diagnosis, risk stratification, and targeted management. Integrating blood pressure patterns with clinical context provides a practical and efficient framework for evaluating various renal conditions in acute care settings.

INTRODUCTION

The relationship between various renal diseases and blood pressure (BP) is central to patient care, particularly in the emergency setting. BP abnormalities, including both hypotension and hypertension (HTN), can serve as either a cause or a consequence of kidney dysfunction. This complex, bidirectional interplay is mediated by key pathophysiological mechanisms such as the renin-angiotensin-aldosterone system (RAAS) activation, volume overload, and systemic inflammatory responses[1]. Understanding these distinct BP profiles is essential for guiding timely diagnosis and appropriate therapeutic interventions across the spectrum of renal conditions[2-4], ranging from acute kidney injury (AKI) to end-stage renal disease (ESRD)[5-7].

The impact of renal dysfunction on BP generally follows two primary pathways. The first is the hypertensive pathway, in which RAAS activation [commonly observed in renal artery stenosis (RAS), renal infarction, and Page kidney], as well as volume expansion resulting from sodium and water retention [seen in chronic kidney disease (CKD), ESRD, and glomerulonephritis (GN)] serve as the primary drivers of renovascular or volume-dependent HTN[1]. The second is the hypotensive pathway, in which volume depletion, early AKI, renal tubular acidosis (RTA), and systemic inflammatory response or shock such as those associated with severe pyelonephritis/sepsis, or acute renal trauma, represent the major mechanisms leading to low BP[2,8].

Distinct BP profiles provide valuable diagnostic and prognostic insights in the emergency department (ED). For instance, hypotension often serves as early AKI, severe infection, or trauma due to compromised renal perfusion. In contrast, HTN is more commonly observed in conditions driven by ischemia or sodium and fluid retention, such as RAS or obstructive uropathy. Recognizing these mechanistically predictable patterns facilitates timely risk stratification and targeted management, with RAAS activation, volume status, and renal ischemia serving as a unifying pathophysiological framework for interpretation[2].

A recent study in 2022 disclosed that among patients with heart failure with reduced ejection fraction and advanced CKD, the use of angiotensin converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ACEI/ARB) was significantly associated with lower all-cause mortality. This survival benefit persisted even in patients with markedly impaired renal function, suggesting that the prognostic advantages of ACEI/ARB therapy are not diminished by advanced kidney disease. Data from the OPTIMIZE-HF registry further demonstrated a substantially lower mortality rate among patients receiving ACEI/ARB therapy compared to those did not receive such treatment (19% vs 33.6%). Importantly, this association remained robust after multivariable adjustment and propensity score matching, supporting an independent protective effect on long-term survival[9].

Current clinical paradigms have shifted toward more intensive hemodynamic management in CKD, as reflected in the latest international consensus. The Kidney Disease: Improving Global Outcomes 2021 Clinical Practice Guideline established a stringent systolic BP (SBP) target of < 120 mmHg for patients with non-dialysis CKD patients, provided that standardized office BP measurements are used. This intensive strategy is based on its demonstrated efficacy in reducing cardiovascular mortality and delaying progression to ESRD. Building upon this foundation, the Kidney Disease: Improving Global Outcomes 2024 Clinical Practice Guideline for the Evaluation and Management of CKD further reinforces the central role of renin-angiotensin system inhibitors (RASi), specifically ACE inhibitors or ARBs, as the cornerstone first-line therapy for patients with HTN and albuminuria. Notably, the 2024 update integrates RASi into a broader multidrug therapeutic framework alongside sodium-glucose co-transporter 2 inhibitors and non-steroidal mineralocorticoid receptor antagonists, underscoring that optimal BP control is now regarded as one component of a comprehensive, and synergistic strategy for mitigating cardiorenal risk[10,11].

BP targets differ substantially between emergency and chronic care settings. Although intensive BP lowering (< 130/80 mmHg) is generally recommended for patients with CKD to reduce cardiovascular risk and delay disease progression, evidence from ED cohorts suggests that acute pharmacologic BP reduction primarily improves short-term outcomes without a clear long-term mortality benefit. These findings highlight the need for context-specific and individualized BP targets based on the clinical scenario[12]. The selection of antihypertensive agents should likewise be individualized according to each patient’s comorbidities, including asthma, diabetes mellitus, cardiovascular diseases, or chronic obstructive pulmonary disease.

We might encounter several conditions of renal disorder and diseases. This minireview aims to summarize disease-specific BP phenotypes, underlying mechanisms, and emergency diagnostic implications across common renal disorders.

AKI AND BP

AKI is characterized by a rapid decline in renal function occurring over hours to days, leading to the accumulation of nitrogenous waste, electrolyte imbalances, and disruptions in fluid homeostasis[2]. Among the numerous clinical factors associated with AKI, BP plays a central and bidirectional role. Mean arterial pressure (MAP) is one of the most critical determinants of renal perfusion. Sustained hypotension – whether caused by sepsis, major trauma, hemorrhage, anesthesia, or cardiogenic shock – can significantly reduce renal blood flow and glomerular filtration. When MAP falls below the kidney’s autoregulatory threshold, typically around 65-75 mmHg, compensatory afferent arteriolar dilation becomes insufficient to preserve glomerular perfusion. In patients with septic shock and pre-existing renal impairment, a higher MAP of approximately 72-82 mmHg may be required to avoid acute kidney insufficiency[13]. Prolonged renal ischemia subsequently leads to tubular epithelial injury, endothelial dysfunction, and ultimately ischemic AKI.

The duration and severity of hypotension are strongly associated with AKI risk. For every additional hour that MAP remains below 70 mmHg, 60 mmHg, and 50 mmHg, the risk of AKI increases by 2%, 5%, and 22%, respectively[3]. HTN is also highly prevalent among patients with AKI – reported at 70% overall, with the highest rates observed in post-renal AKI (85%), followed by intrinsic renal AKI (75%) and pre-renal AKI (30%)[4]. Collectively, these findings suggest that both hypotension and HTN may contribute to the development and progression of AKI, while AKI itself can further impair hemodynamic regulation and exacerbate BP instability.

Conversely, acute severe HTN can also precipitate AKI through distinct pathophysiological mechanisms. Abrupt elevations in BP can overwhelm the kidney’s autoregulatory capacity, leading to glomerular hyperperfusion, capillary injury, and disruption of the glomerular filtration barrier[14]. In addition, chronic poorly controlled HTN predisposes patients to AKI by promoting nephrosclerosis, reducing nephron reserve, and increasing susceptibility to secondary insults such as volume depletion or exposure to nephrotoxic agents[5].

CKD AND BP

CKD and BP are closely interconnected through a complex, bidirectional relationship. HTN is not only a major cause of CKD but also one of its most common and clinically significant complications[15]. The prevalence of HTN among individuals with CKD is substantially higher than in the general population and increases progressively with CKD severity, with overall rates estimated at 80%-85%. In patients with CKD, HTN markedly increases the risk of cardiovascular events, including myocardial infarction, heart failure, and stroke[16]. At the same time, HTN remains one of the leading causes of CKD worldwide. Sustained elevations in BP induce both structural and functional alterations in the renal microvasculature, including arteriolar thickening, glomerulosclerosis, and progressive ischemic nephron loss. Elevated SBP further accelerates renal function decline. For example, in patients with SBP greater than 160 mmHg, the annual decline in estimated glomerular filtration rate approximates -2.09 mL/minute/1.73 m². Longitudinal studies have further demonstrated that every 10-mmHg increase in SBP is associated with a 39% higher risk of requiring kidney replacement therapy[17]. Over time, patients with persistently uncontrolled HTN may develop hypertensive nephrosclerosis, characterized by interstitial fibrosis, glomerular ischemia, and eventual glomerular collapse.

Once CKD is established, impaired renal regulation of fluid and sodium excretion frequently results in volume expansion, which serves as a major contributor of HTN in this population. The loss of functional nephron mass increases renal sensitivity to sodium intake, such that even modest dietary sodium loads can lead to elevations in BP. Additionally, CKD is associated with enhanced activation of the RAAS, sympathetic nervous system activation, and endothelial dysfunction – all of which contribute to persistent vasoconstriction and elevated systemic vascular resistance[1]. The relationship between CKD and BP is further complicated by the presence of proteinuria, which can independently exacerbate glomerular injury and accelerate the progression of renal disease. Furthermore, many patients with CKD exhibit “salt-sensitive HTN”, in which BP responds markedly to changes in sodium balance[18].

As CKD progresses to more advanced stages, BP control becomes increasingly challenging and patients often require combination therapy with multiple antihypertensive agents to achieve guideline-recommended targets. Effective BP management remains one of the most important interventions for slowing CKD progression. RAAS inhibitors, including ACE inhibitors and ARBs, are considered first-line therapies because they not only lower BP, but also reduce proteinuria and confer renoprotective effects. Dietary sodium restriction, weight control, and individualized BP targets – often < 130/80 mmHg – are essential components of comprehensive care[19]. CKD and HTN form a self-perpetuating cycle in which elevated BP accelerates renal injury, while progressive kidney dysfunction further exacerbates HTN. Breaking this vicious cycle through optimal BP control is essential for preserving renal function and improving long-term clinical outcomes.

ESRD AND BP

ESRD, the terminal stage of CKD, is characterized by near-complete loss of renal function requiring dialysis or kidney transplantation. In this advanced state, BP regulation becomes profoundly impaired. HTN is highly prevalent among patients with ESRD, and represents a major contributor to cardiovascular morbidity and mortality. Lacson and Lazarus[6] suggested that the optimal BP range for improving survival in this population may be higher than that recommended by current guidelines, proposing targets SBP ranges of 140-160 mmHg before hemodialysis (HD) and 135-154 mmHg after HD. Meanwhile, dialysis-related hemodynamic fluctuations may also precipitate episodes of intradialytic hypotension, further highlighting the complex and often unstable relationship between ESRD and BP[20].

HTN in ESRD is multifactorial, with chronic volume overload – resulting from impaired sodium and water excretion – being a major contributor[21]. Even with regular HD, achieving an accurate “dry weight” is difficult, and excess extracellular fluid elevates BP and increases cardiac workload. Additional mechanisms include RAAS activation, heightened sympathetic tone, endothelial dysfunction, arterial stiffness, and vascular calcification, all of which promote persistent HTN in this population[22]. In HD patients, BP fluctuates substantially before, during, and after treatment. While ultrafiltration typically lowers BP, overly rapid fluid removal may cause intradialytic hypotension, manifesting as dizziness, cramps, nausea, or syncope and potentially impairing vital organ perfusion. Conversely, interdialytic fluid gain often drives BP increases between sessions. Peritoneal dialysis tends to offer more stable BP control, though volume overload remains a concern as membrane transport characteristics change. Kidney transplant recipients face different challenges, particularly HTN secondary to calcineurin inhibitors and other immunosuppressive agents[23].

Managing BP in ESRD requires a multifaceted approach. Essential strategies include the precise assessment of dry weight, dietary sodium restriction, individualized dialysis prescriptions, and the use of antihypertensive medications – including RAAS inhibitors, beta-blockers, and calcium channel blockers – Adequate BP control is critical, given that cardiovascular disease remains the leading cause of death in ESRD patients[24]. ESRD profoundly disrupts normal BP regulation, leading to a complex interplay of HTN, volume overload, vascular dysfunction, and dialysis-related hemodynamic instability. Consequently, effective BP management serves as a cornerstone for improving outcomes in the ESRD population.

GN AND BP

GN encompasses a group of disorders characterized by glomerular inflammation, leading to impaired filtration, proteinuria, hematuria, and varying degrees of renal dysfunction. BP abnormalities are prevalent in GN and play a significant role in both its pathogenesis and clinical outcomes. HTN not only reflects the severity of glomerular injury but also accelerates disease progression, thereby contributing to long-term renal and cardiovascular complications. For instance, mild to moderate HTN occurs in more than 75% of patients with acute forms of GN, such as poststreptococcal GN[25]. The pathogenesis of HTN in GN is primarily driven by reduced glomerular filtration rate and subsequent sodium and water retention. As inflammation disrupts the glomerular capillary network, filtration efficiency is compromised, leading to extracellular volume expansion, and this is a key factor in BP elevation. In addition, activation of the RAAS, triggered by localized glomerular ischemia, promotes vasoconstriction and increases systemic vascular resistance. Synergistically, these mechanisms produce the characteristic HTN observed in both acute and chronic forms of GN[25].

Certain types of GN, such as rapidly progressive GN (RPGN) and lupus nephritis, are strongly predisposed to severe HTN. In addition, a retrospective study from Morocco reported that 66.3% of acute post-streptococcal GN patients have HTN[26]. In these conditions, rapid loss of functioning nephrons heightens the kidney’s sensitivity to sodium intake, rendering BP control exceptionally challenging. Persistent HTN exacerbates glomerular injury by increasing intraglomerular pressure, promoting further proteinuria, and accelerating the progression toward CKD. Proteinuria itself serves as both a marker and mediator of ongoing tissue damage, establishing a vicious cycle between HTN and progressive renal impairment[27]. In some cases of acute GN, such as post-streptococcal GN, children may present with acute hypertensive episodes or hypertensive encephalopathy, reflecting abrupt changes in renal function and fluid balance[28]. Conversely, early or mild forms of GN may present with normal BP, emphasizing the heterogeneous clinical spectrum of this disease.

Effective management of HTN is a critical component of GN treatment. RAAS inhibitors, including ACE inhibitors and ARBs, are particularly beneficial because they not only lower systemic BP but also reduce intraglomerular pressure and proteinuria, offering significant reno-protective effects. Dietary sodium restriction, optimal fluid management, and vigilant monitoring of renal function are equally important. In immune-mediated GN, controlling the underlying inflammatory process with corticosteroids or other immunosuppressive therapies can further stabilize BP[29]. For patients with chronic GN presenting with either micro- or macroalbuminuria, a stricter BP target of ≤ 130/80 mmHg may be appropriate, provided they are not elderly and do not exhibit high cardiovascular risk profiles[25]. Ultimately, GN and BP are inextricably linked through overlapping pathways involving volume overload, RAAS activation, and progressive glomerular injury. Timely and intensive BP control remains essential for preserving renal function and improving long-term outcomes in patients with GN.

KIDNEY PARENCHYMA INJURY (RENAL TRAUMA, HEMATOMA) AND BP

Renal trauma from blunt injuries (e.g., motor vehicle accidents) or penetrating wounds can result in renal hematoma, and the associated BP changes are important indicators of injury severity and hemodynamic stability. Both hypotension and HTN may occur, each carrying distinct clinical implications. In the acute phase, hypotension is the primary concern, as it frequently reflects significant blood loss or multi-organ injury. A rapidly expanding perirenal or retroperitoneal hematoma can sequester large volumes of blood, thereby reducing effective circulating volume and leading to shock. Persistent hypotension despite resuscitation suggests high-grade renal laceration, renal pedicle injury, or concurrent intra-abdominal bleeding necessitating urgent imaging or surgical evaluation[30]. Conversely, arterial HTN may result as a complication of trauma to the kidney, with an incidence as high as 40%; that is, it may arise from renal compression caused by a perinephric hematoma or chronic peri-renal scarring, which ultimately leads to localized ischemia and segmental arterial stenosis[31].

Conversely, renal trauma can also lead to HTN, both acutely and in the delayed period. A primary underlying mechanism is the compression of the renal parenchyma by a hematoma, known as the Page kidney phenomenon – which increases intrarenal pressure, reduces renal perfusion, and activates the RAAS. This activation results in systemic vasoconstriction and sustained HTN. If left untreated, Page kidney-associated HTN can persist chronically and contribute to progressive renal dysfunction[32]. Documenting perirenal compression via radiological findings remains critical for a definitive diagnosis. Management includes draining the hematoma or performing a nephrectomy; BP usually stabilizes quickly thereafter. Additionally, post-traumatic HTN may arise from renal artery injury, thrombosis, or dissection, all of which impair renal perfusion and stimulate RAAS activity[33].

Monitoring BP is therefore essential in the evaluation and follow-up of patients with renal trauma. Hypotension indicates ongoing bleeding and may necessitate intervention, whereas new-onset or worsening HTN suggests hematoma expansion, subcapsular compression, or vascular injury. Imaging – particularly contrast-enhanced computed tomography – is crucial for correlating BP changes with the extent of renal damage. Management strategies are strictly tailored to the underlying mechanism. Fluid and blood product resuscitation address hypotension, while HTN secondary to Page’s kidney may require antihypertensive therapy or hematoma drainage. Ultimately, severe vascular injuries or expanding hematomas may necessitate surgical repair or angioembolization[34].

PYELONEPHRITIS AND BP

Pyelonephritis, an infection of the renal parenchyma and collecting system, is typically characterized by fever, flank pain, chills, and systemic inflammation. Although BP abnormalities are not always the primary clinical manifestation, pyelonephritis can significantly influence BP through mechanisms involving systemic infection, renal perfusion, and inflammatory responses. Both hypotension and HTN may occur depending on the severity of infection and underlying renal physiology. HTN has been reported in only 7% of patients with pyelonephritis[35]. In acute pyelonephritis, hypotension is most often associated with severe infection or sepsis. Bacterial invasion of the renal tissue can trigger systemic inflammatory response syndrome, resulting in widespread vasodilation, capillary leakage, and decreased systemic vascular resistance. As the infection progresses to septic shock, patients may develop profound hypotension despite adequate fluid resuscitation, representing a life-threatening emergency that requires prompt antibiotic therapy and vasoactive support. In this context, hypotension indicates severe disease and may contribute to AKI by compromising renal perfusion. A Republic of Korea study reported that 62.8% pyelonephritis cases developed AKI[7].

Management of pyelonephritis focuses on treating the underlying infection while maintaining hemodynamic stability. Patients with hypotension require aggressive fluid resuscitation, broad-spectrum antibiotics, and close monitoring for septic shock. When HTN is present, inhibition of the RAAS combined with appropriate antimicrobial therapy often lead to BP improvement as inflammation resolves. In cases of chronic HTN secondary to renal scarring, long-term antihypertensive therapy may be necessary[36]. Pyelonephritis can affect BP through mechanisms of infection-induced hypotension. Recognizing these relationships is essential for timely diagnosis, appropriate management, and prevention of long-term renal complications.

RAS AND BP

Atherosclerosis is the leading cause of RAS. Atherosclerotic RAS is associated with three major clinical consequences – renovascular HTN, ischemic nephropathy, and cardiac destabilization syndrome – each carrying substantial healthcare implications. Certain subgroups of patients with atherosclerotic RAS experience favorable outcomes after percutaneous transluminal renal artery stenting. For example, patients who demonstrated improved renal function following percutaneous transluminal renal artery stenting were reported to have a 45% survival advantage compared with those whose renal function did not improve[37]. RAS, caused primarily by atherosclerosis or, less commonly, by fibromuscular dysplasia, is characterized by narrowing of one or both renal arteries. This reduction in renal perfusion activates hormonal and hemodynamic pathways that significantly influence BP. RAS is a classic cause of secondary HTN and often presents as severe, refractory, or abrupt-onset HTN[38].

The pathophysiology of HTN in RASis primarily mediated by activation of the RAAS. When renal blood flow decreases, the affected kidney perceives this as systemic hypotension and releases renin from the juxtaglomerular apparatus. Renin then converts angiotensinogen to angiotensin I, which is subsequently converted to angiotensin II – a potent vasoconstrictor. Angiotensin II increases systemic vascular resistance and stimulates aldosterone secretion, promoting sodium and water retention. Collectively, these mechanisms lead to sustained elevation of BP[38]. In unilateral RAS, the contralateral kidney may initially compensate by enhancing sodium, but chronic exposure to high BP eventually causes pressure natriuresis impairment and widespread HTN[39].

In bilateral RAS, or in stenosis affecting a solitary functioning kidney, volume-dependent HTN becomes particularly pronounced. Reduced perfusion in both kidneys limits natriuresis, leading to volume expansion and severe, treatment-resistant HTN. These patients are also vulnerable to AKI, particularly when given ACE inhibitors or ARBs, which further lower intraglomerular pressure in already under-perfused kidneys.

BP abnormalities provide important diagnostic clues. Patients may present with malignant HTN, recurrent flash pulmonary edema, or marked BP variability. Suspicion for RAS increases when HTN is resistant to three or more medications, when an abdominal bruit is detected, or when renal function declines after initiating RAAS blockade. RAS and BP are tightly interconnected through RAAS activation, impaired perfusion, and volume retention. Early diagnosis and appropriate BP management are essential to preventing long-term cardiovascular and renal complications[40].

RENAL CALCULUS AND BP

Renal calculi (kidney stones) are crystalline deposits within the renal collecting system. Although traditionally viewed as a urological condition, increasing evidence links nephrolithiasis with BP alterations. This interaction is multifactorial, involving metabolic disturbances, obstruction, inflammation, and chronic renal injury. HTN and nephrolithiasis frequently coexist; however, stone composition or disease severity does not appear to predict HTN risk[38].

Epidemiological data consistently show a higher prevalence of HTN among patients with nephrolithiasis. Several pathophysiological mechanisms may contribute, including metabolic abnormalities – such as hypercalciuria, insulin resistance, and heightened sympathetic activity – that are also linked to elevated BP. Shock wave lithotripsy has been associated with a 40% increased risk of HTN (hazard ratio = 1.40; 95%CI: 1.19-1.66), though a Mayo Clinic study reported a nonsignificant 58% increase[41].

Renal obstruction caused by a ureteral stone can acutely influence BP. When a stone obstructs urinary flow, intrarenal pressure rises, leading to hydronephrosis. This increase in pressure may activate the RAAS, resulting in vasoconstriction and transient HTN. In some patients, relief of obstruction – either through spontaneous stone passage or surgical intervention – leads to normalization of BP, highlighting the role of obstruction-induced RAAS activation[42].

Recurrent nephrolithiasis may also cause chronic structural injury to the kidney. Repeated episodes of obstruction, infection, or inflammation may lead to renal scarring, reduced nephron mass, and impaired sodium handling. A high-salt diet has a promotive effect on salt-sensitive HTN and urolithiasis[43]. Renal calculi and BP are interconnected through pathways involving obstruction, metabolic dysfunction, inflammation, and renal scarring. Recognition of this relationship and timely intervention are essential for optimizing both renal and cardiovascular outcomes.

RENAL INFARCTION AND BP

Renal infarction, defined as ischemic necrosis of renal tissue due to obstruction of renal arterial blood flow, is an uncommon but clinically important condition. Structural abnormalities of the renal artery represent the most common underlying cause (81.2%), and renal infarction may result from thromboembolism, in-situ thrombosis, renal artery dissection (40.8%), hypercoagulable states, or traumatic injury[44]. The relationship between renal infarction and BP is bidirectional: Alterations in BP can predispose patients to renal infarction, while renal infarction itself may induce significant – and sometimes persistent – HTN[44].

The pathophysiology of post-infarction HTN is primarily driven by reduced renal perfusion. When renal tissue becomes ischemic, the affected kidney perceives the reduced perfusion as systemic hypotension. Juxtaglomerular cells then release renin, activating the RAAS. Elevated angiotensin II causes systemic vasoconstriction, while aldosterone promotes sodium and water retention, together driving BP upward. This mechanism parallels the physiology of RAS, but in renal infarction, the loss of viable renal tissue can make BP more resistant to correction. In one cohort study, up to 54.5% of patients with renal infarction developed malignant HTN[38,45].

New-onset or worsening HTN serves as a key clinical indicator of renal infarcts. In unilateral infarction, the contralateral kidney may compensate, but persistent RAAS activation can eventually lead to generalized HTN. Conversely, in bilateral infarction or in patients with a solitary functioning kidney, the BP elevation can be severe and rapidly progressive. These patients may also develop AKI due to a reduction in overall renal perfusion and filtration capacity. Crucially, the relationship between BP abnormalities and renal infarction is bidirectional. Severe HTN, particularly malignant HTN, may cause endothelial injury and promote thrombosis within renal arteries. Long-standing HTN also accelerates atherosclerosis, increasing the risk of arterial occlusion and embolic events. Thus, uncontrolled BP is both a cause and a consequence of renal infarction.

Diagnosis often relies on contrast-enhanced computed tomography, which can reveal wedge-shaped perfusion defects typical of infarction. Clinically, the combination of flank pain, hematuria, elevated lactate dehydrogenase, and sudden HTN should raise suspicion[46]. Management centers on restoring perfusion when possible, preventing further thromboembolic events, and controlling BP. Anticoagulation is often essential, while RAAS inhibitors – ACE inhibitors or ARBs – may help counteract renin-driven HTN. However, care must be taken in patients with extensive infarction or impaired renal function. Ultimately, renal infarcts profoundly influence BP through RAAS-mediated pathways, while HTN itself increases the risk of renal ischemic injury.

RTA AND BP

RTA refers to a group of disorders characterized by impaired acid secretion or bicarbonate reabsorption in the renal tubules, resulting in chronic metabolic acidosis. Unlike many renal diseases in which BP abnormalities are common, RTA has a more nuanced and variable relationship with BP. While most classical forms of RTA do not directly cause HTN, certain pathophysiological mechanisms associated with RTA can influence BP, and in some cases, secondary complications may alter cardiovascular regulation.

In distal (type 1) RTA, impaired hydrogen ion secretion in the distal nephron leads to metabolic acidosis, hypokalemia, and an inability to acidify urine. Patients typically maintain normal or low BP due to mild volume depletion. Hypokalemia commonly causes vasodilation and reduces vascular responsiveness, which may contribute to normotension. However, chronic acidosis can lead to nephrocalcinosis, kidney stones, and progressive loss of renal parenchyma. Over time, the development of renal scarring may increase salt sensitivity, predisposing patients to HTN secondary to CKD. Thus, although distal RTA itself is not hypertensive, long-term structural renal injury may eventually contribute to elevated BP[8,47].

Proximal (type 2) RTA involves impaired bicarbonate reabsorption in the proximal tubules. Patients may experience volume depletion due to bicarbonaturia and osmotic diuresis[47]. This typically results in normal or slightly reduced BP. Proximal RTA often occurs as part of Fanconi syndrome, which is characterized by phosphate wasting, glucosuria, and aminoaciduria. If progressive renal injury occurs, BP may increase over time due to reduced nephron mass, similar to other CKD-related hypertensive mechanisms.

Hyperkalemic (type 4) RTA, most commonly caused by hypoaldosteronism or aldosterone resistance, abnormal excretion of acid and K+ in the collecting duct, or hyperkalemic type 4 RTA may be caused by medications, including K+-sparing diuretics which lead to hyperkalemic acidosis to have a more direct and clinically relevant relationship with BP[47]. These patients frequently have underlying diabetic nephropathy, interstitial nephritis, or obstructive uropathy. Hyporeninemic hypoaldosteronism leads to impaired sodium reabsorption and reduced potassium and hydrogen secretion. Although hyperkalemia is the hallmark, many patients have low or normal BP because aldosterone deficiency limits sodium retention. However, in diabetic kidney disease or advanced interstitial nephropathy, coexisting CKD may drive the development of HTN independent of the tubular defect.

Type I and II RTA cause urinary loss of bicarbonate, potassium, and sodium. This leads to dehydration and volume depletion, resulting in low BP, especially orthostatic hypotension. RTA is often associated with underlying conditions such as autoimmune diseases, CKD, or diabetes. When RTA coexists with CKD, late-stage CKD may cause HTN due to sodium and water retention. Type IV RTA inherently tends toward hypotension, but it frequently occurs in diabetic nephropathy or other renal parenchymal diseases that themselves commonly cause HTN. Thus, patients may present with both RTA and high BP. Overall, RTA intrinsically predisposes patients to hypotension; however, when it is secondary to CKD or diabetes, the hypertensive effects of these underlying diseases may mask or counterbalance the hypotensive tendency caused by RTA.

The impact of renal dysfunction on BP follows two primary pathways, one is RAAS activation (seen in RAS, renal infarction, and Page kidney) and volume expansion/sodium and water retention (seen in CKD, ESRD, and GN) are the main mechanisms driving renovascular or volume-dependent HTN[3,6,22,24]. Another is volume depletion (early AKI, RTA) and systemic inflammatory response or shock (severe pyelonephritis/sepsis, acute renal trauma) are the main mechanisms leading to low BP[13,34]. A summary is provided in Table 1[2-4,6,7,13,18-21,25-27,35,38,41-43], outlining variable BP patterns across renal conditions encountered in the ED. Overall, the relationship between renal status and BP resembles a physiological seesaw, dynamically shifting between RAAS-driven and volume-overload HTN on one side, and hypotension driven by hemorrhage, shock, or severe volume depletion on the other, as illustrated in the accompanying Figure 1.

Figure 1 The relationship between renal status and blood pressure. RAAS: Renin-angiotensin-aldosterone system; CKD: Chronic kidney disease; ESRD: End-stage renal disease; HTN: Hypertension; AKI: Acute kidney injury. The figure was generated using NotebookLM (https://notebooklm.google.com/). Because the textual elements are displayed separately from the graphical components, the text can be independently edited and modified by the authors, making the figure fully editable. Both the intellectual content and the final figure design were created and customized by the authors, and the figure represents original author-generated work.

Table 1 Blood pressure phenotypes, mechanisms, and emergency department management in renal diseases.

Renal disease	BP phenotype	Key pathophysiology	ED diagnostic clues	Immediate ED management	Ref.
CKD	Persistent HTN (± refractory)	Na+/water retention; RAAS activation	Known CKD, Cr (increase), anemia	Gradual BP reduction (≤ 25%); start IV CCB (nicardipine); avoid overcorrection	Dylewska et al[4], Jeon et al[7], Nakazawa et al[43]
AKI	Variable: HTN or hypotension	Volume overload or hypoperfusion	Rapid Cr (increase), oliguria	Treat cause: Fluids (if hypovolemic) or diuretics; avoid nephrotoxins	Yu et al[2], Lehman et al[3], Badin et al[13]
GN	Severe HTN	Inflammation + RAAS activation	Hematuria, proteinuria, edema	IV antihypertensives; consider immunologic workup	Ihm[25], Tizki et al[26]
Nephrotic syndrome	Mild-moderate HTN	Hypoalbuminemia to edema	Massive proteinuria, edema	Diuretics; cautious BP control	Bovée et al[18], Pugh et al[19], Ihm[25], Kidney Disease: Improving Global Outcomes (KDIGO) Glomerular Diseases Work Group[27]
RAS	Resistant HTN	Renal ischemia to RAAS overactivation	Abdominal bruit, flash pulmonary edema	Avoid ACEI if bilateral; imaging referral	Shen et al[38]
Uremia (ESRD)	Severe HTN or hypotension	Toxin accumulation	Uremic symptoms	Urgent dialysis indication	Lacson and Lazarus[6], Davenport[20], Flythe and Bansal[21]
Obstructive uropathy	HTN (early) to hypotension (late)	Back pressure + renal dysfunction	Hydronephrosis (US)	Relieve obstruction (catheter, stent)	Kittanamongkolchai et al[41], Chalisey and Karim[42]
Sepsis-associated AKI	Hypotension	Vasodilation + capillary leak	Infection signs, lactate (increase)	Early fluids + vasopressors	Tsuchida et al[35]

RAAS: Renin-angiotensin-aldosterone system; CKD: Chronic kidney disease; ESRD: End-stage renal disease; HTN: Hypertension; AKI: Acute kidney injury; ED: Emergency department; CCB: Calcium channel blocker; BP: Blood pressure; GN: Glomerulonephritis; ACEI: Angiotensin converting enzyme inhibitors; US: Ultrasonographic.

CONCLUSION

Clinically, BP abnormalities in renal diseases represent a dynamic and clinically meaningful spectrum that reflects diverse underlying pathophysiological processes. Despite their heterogeneity, these hemodynamic patterns are largely predictable and can be interpreted through key mechanisms such as RAAS activation, volume status alterations, and renal perfusion changes. In the ED, recognizing whether hypotension reflects renal hypoperfusion, sepsis, or trauma-related hemorrhage, or whether HTN indicates volume overload, ischemia, or renovascular pathology, is critical for rapid diagnosis and risk stratification. Integrating BP patterns with the overall clinical context not only enhances diagnostic accuracy but also facilitates timely, targeted management. Ultimately, a mechanistic understanding of these hemodynamic responses provides a practical and unifying framework for optimizing outcomes in patients with diverse renal conditions, as we introduced.