Idiopathic myointimal hyperplasia of mesenteric veins mimicking steroid-refractory ulcerative colitis: A case report

Abstract

BACKGROUND

Idiopathic myointimal hyperplasia of mesenteric veins (IMHMV) is a rare, non-thrombotic venous occlusive disease that causes chronic intestinal ischemia and frequently mimics inflammatory bowel disease, particularly ulcerative colitis. Because clinical, endoscopic, and radiologic findings are nonspecific, IMHMV is often misdiagnosed, leading to delayed definitive treatment.

CASE SUMMARY

A 65-year-old man with a history of living-donor liver transplantation presented with a 6-month history of watery diarrhea and abdominal pain. He was receiving tacrolimus and mycophenolate mofetil for immunosuppression. Colonoscopy demonstrated continuous colitis extending from the mid-transverse colon to the rectum, and mucosal biopsies showed only nonspecific chronic inflammation. Despite treatment with mesalazine, corticosteroids, and filgotinib, the patient showed progressive clinical deterioration and developed massive hematochezia requiring emergent open subtotal colectomy with end transverse colostomy and rectal stump preservation. Histopathologic examination of the resected specimen revealed marked myointimal hyperplasia of mesenteric veins with near-complete luminal obliteration and subendothelial fibrin deposition, while arterial structures were preserved, confirming IMHMV. Postoperatively, inflammation recurred in the rectal stump and improved with topical mesalazine therapy.

CONCLUSION

IMHMV should be considered in patients with steroid-refractory colitis and nonspecific biopsy findings. This case highlights the diagnostic limitations of mucosal biopsy, the importance of histopathologic confirmation, and the need for careful interpretation of postoperative rectal inflammation, in which diversion colitis and underlying inflammatory bowel disease may overlap.

Key Words: Idiopathic myointimal hyperplasia of mesenteric veins; Ulcerative colitis; Inflammatory bowel disease; Mesenteric venous disease; Diversion colitis; Colonic ischemia

Core Tip: Idiopathic myointimal hyperplasia of mesenteric veins is a rare venous occlusive disease that can closely mimic ulcerative colitis and lead to misdiagnosis. This case demonstrates progressive steroid-refractory colitis unresponsive to medical therapy, ultimately requiring surgery for definitive diagnosis. Postoperative rectal inflammation created a diagnostic dilemma between diversion colitis and possible underlying inflammatory bowel disease. This report highlights the importance of considering vascular etiologies in refractory colitis and cautiously interpreting postoperative endoscopic findings.

INTRODUCTION

Idiopathic myointimal hyperplasia of mesenteric veins (IMHMV) is an uncommon vascular disorder first described by Genta and Haggitt[1] in 1991. It is characterized by smooth muscle proliferation within the venous intima, resulting in venous luminal narrowing without arterial involvement or thrombotic occlusion. The resulting non-thrombotic ischemia predominantly affects the left colon, especially the rectosigmoid region, and occurs mainly in middle-aged to elderly men[1,2].

Clinically, IMHMV presents with abdominal pain, diarrhea, and hematochezia, closely resembling ulcerative colitis (UC) or ischemic colitis[2,3]. Endoscopic findings are nonspecific and may include erythema, friability, ulceration, edema, and segmental or continuous colitis. Because routine mucosal biopsies usually reveal only nonspecific chronic or ischemic-type inflammation, preoperative diagnosis is difficult, although characteristic venous abnormalities can occasionally be detected in deep biopsy specimens[4-7].

We report a liver transplant recipient who presented with chronic steroid-refractory colitis initially treated as UC. Subsequent colectomy revealed IMHMV, and postoperative follow-up suggested a possible coexisting UC component. This case underscores that IMHMV should be considered in the differential diagnosis of refractory colitis with nonspecific biopsy findings, including in immunosuppressed patients.

CASE PRESENTATION

Chief complaints

A 65-year-old man presented with a 6-month history of watery diarrhea occurring approximately 10 times per day, accompanied by cramping lower abdominal pain that was more prominent in the morning and evening.

History of present illness

The patient denied fever, hematochezia, significant weight loss, or extraintestinal manifestations. His symptoms had initially been managed conservatively with probiotics and antispasmodics under the impression of irritable bowel syndrome; however, there was no clinical improvement, and he was admitted for further evaluation.

History of past illness

His medical history was notable for chronic hepatitis B and living-donor liver transplantation performed in 2015 for hepatitis B-related cirrhosis. He had been maintained on tacrolimus (3.5 mg once daily) and mycophenolate mofetil (500 mg twice daily) as post-transplant immunosuppression. He had no history of hypertension, diabetes mellitus, tuberculosis, or other chronic illnesses.

Personal and family history

He was a lifelong nonsmoker, did not consume alcohol, and had no relevant family history.

Physical examination

On admission, he was afebrile and hemodynamically stable. Physical examination revealed a soft abdomen with mild lower abdominal tenderness but no rebound tenderness or guarding.

Laboratory examinations

Laboratory tests showed a white blood cell count of 8600/μL, hemoglobin 12.2 g/dL, platelet count 319000/μL, and C-reactive protein 8 mg/L. Fecal calprotectin was elevated to 233 mg/kg. Stool polymerase chain reaction detected enteropathogenic Escherichia coli. Blood polymerase chain reaction tests for cytomegalovirus, herpes simplex virus, and Epstein-Barr virus were negative. Biopsy specimens obtained during colonoscopy revealed nonspecific chronic inflammation without crypt architectural distortion, granulomas, or viral inclusions.

Imaging examinations

Colonoscopy at presentation revealed continuous mucosal inflammation characterized by edema, erythema, and friability extending from the transverse colon through the descending and sigmoid colon to the rectum. No definite deep ulceration was identified, and a relatively sharp demarcation from adjacent normal mucosa was noted at the proximal extent of involvement (Figure 1). Contrast-enhanced abdominal computed tomography (CT) demonstrated diffuse colonic wall thickening with pericolonic fat stranding involving the descending colon, sigmoid colon, and rectum, corresponding to the distribution of inflammation observed on colonoscopy (Figure 2).

Figure 1 Initial colonoscopic findings. Colonoscopy at presentation revealed continuous mucosal inflammation characterized by edema, erythema, and friability extending from the transverse colon through the descending and sigmoid colon to the rectum. No definite deep ulceration was identified, and a relatively sharp demarcation from adjacent normal mucosa was noted at the proximal extent of involvement. A: Transverse colon; B: Descending colon; C: Sigmoid colon; D: Rectum.

Figure 2 Abdominal computed tomography findings. Contrast-enhanced abdominal computed tomography demonstrated diffuse colonic wall thickening with pericolonic fat stranding involving the descending colon, sigmoid colon, and rectum (arrows). These findings corresponded to the distribution of inflammation observed on colonoscopy. A: Descending colon; B: Sigmoid colon; C: Rectum.

MULTIDISCIPLINARY EXPERT CONSULTATION

The differential diagnosis included UC, infectious colitis, mycophenolate mofetil-induced colitis, and ischemic colitis. Infectious colitis was considered because of the positive stool polymerase chain reaction result; however, the chronic course and continuous rectal involvement were not typical of acute infection. Mycophenolate mofetil-induced colitis was also considered but was thought to be less likely because the patient had tolerated long-term therapy without prior gastrointestinal complications. Ischemic colitis remained a possibility, although the continuous distribution with rectal involvement was less typical. Based on the continuous mucosal involvement, elevated inflammatory markers, and nonspecific chronic inflammation on biopsy, UC was regarded as the most likely working diagnosis. The patient was subsequently discussed with inflammatory bowel disease (IBD) specialists because of the diagnostic uncertainty.

FINAL DIAGNOSIS

IMHMV.

TREATMENT

Initial treatment included oral mesalazine (4 g/day), empirical intravenous antibiotics, and antiviral therapy. The dose of mycophenolate mofetil was reduced, while tacrolimus was maintained. Despite these measures, diarrhea persisted and inflammatory markers increased. Because of persistent diarrhea and worsening inflammatory markers despite initial therapy, follow-up sigmoidoscopy was performed, demonstrating interval worsening of colonic inflammation. Intravenous methylprednisolone (50 mg/day) was therefore initiated for presumed acute severe UC. Although a transient partial response was observed, hematochezia subsequently developed with progressive clinical deterioration. Repeat sigmoidoscopy demonstrated marked progression of colonic inflammation despite corticosteroid therapy, with extensive irregular deep ulcerations covered by thick exudate in the transverse and descending colon. Similar severe ulcerative lesions were observed in the sigmoid colon and rectum, accompanied by areas of mucosal denudation and suspected vascular exposure, indicating severe progression of disease (Figure 3).

Figure 3 Follow-up sigmoidoscopy demonstrating marked progression of ulcerative lesions. Follow-up sigmoidoscopy performed for hematochezia showed marked worsening of colonic inflammation despite ongoing medical therapy. The transverse colon and descending colon demonstrated extensive mucosal ulceration with irregular, deep ulcers covered by thick exudate. Similar findings were observed in the sigmoid colon and rectum, where ulcerations appeared more extensive and deeper, with areas of mucosal denudation and suspected vascular exposure. These findings indicate severe progression of disease activity despite corticosteroid and subsequent filgotinib therapy. A: Transverse colon; B: Descending colon; C: Sigmoid colon; D: Rectum.

Because the patient declined injectable biologic agents, including anti-tumor necrosis factor agents and vedolizumab, oral filgotinib (200 mg/day) was initiated as rescue therapy. Filgotinib was selected because rapid oral induction was required and the patient refused injectable treatment; the potential risks of infection or viral reactivation associated with additional biologic immunosuppression were also considered. At that time, diagnostic uncertainty remained among UC, mycophenolate mofetil-induced colitis, and ischemic colitis. Transient clinical improvement was observed after filgotinib initiation. However, 9 days after starting filgotinib, the patient developed massive hematochezia with hypotension. Because of hemodynamic instability and ongoing bleeding, emergent open subtotal colectomy with end transverse colostomy and rectal stump preservation was performed.

OUTCOME AND FOLLOW-UP

Gross examination of the resected specimen revealed diffuse inflammatory involvement from the mid-transverse colon to the rectum, with extensive ulceration and hemorrhagic changes. The sigmoid colon showed particularly severe, near-necrotizing changes, consistent with fulminant colitis (Figure 4). Histopathologic examination revealed marked myointimal hyperplasia of mesenteric veins with near-complete luminal obliteration. Arterial structures were preserved without intimal thickening, and small venules showed subendothelial fibrin deposition. No evidence of vasculitis or thrombotic occlusion was identified. These findings were diagnostic of IMHMV (Figure 5). Following the pathologic diagnosis, mesalazine and filgotinib were discontinued, and the patient improved postoperatively.

Figure 4 Gross findings of the resected colon. Gross examination of the resected specimen demonstrated diffuse inflammatory changes extending from the mid-transverse colon to the rectum. The mucosa showed extensive ulceration, edema, and areas of hemorrhage, with particularly severe involvement of the sigmoid colon, where near-necrotizing changes were observed. These findings are consistent with fulminant colitis.

Figure 5 Histopathologic findings of the resected colon consistent with idiopathic myointimal hyperplasia of mesenteric veins. A: A mesenteric artery showing a preserved normal wall architecture without intimal thickening (white arrow), × 100; B: A mesenteric vein demonstrating marked myointimal hyperplasia with near-complete luminal obliteration (orange arrows), × 100; C: Small venules exhibiting subendothelial fibrin deposition, seen as eosinophilic material beneath the endothelium (arrowhead), × 40. These findings are characteristic of idiopathic myointimal hyperplasia of mesenteric veins, highlighting selective venous involvement with arterial sparing.

At 3 months after surgery, follow-up sigmoidoscopy showed mild inflammation confined to the rectal stump without definite ulceration (Figure 6A). However, at 12 months after surgery, repeat sigmoidoscopy demonstrated recurrent inflammation with newly developed shallow ulcerations in the rectal stump (Figure 6B). Biopsy revealed chronic colitis with cryptitis, lymphoplasmacytic infiltration of the lamina propria, glandular distortion, and mucin depletion, without granulomas. In contrast, the colostomy segment and remaining colon were endoscopically normal. Topical mesalazine suppositories (1 g/day) were resumed, resulting in symptomatic improvement within 3-4 days. The postoperative course suggested a possible coexisting UC component superimposed on IMHMV.

Figure 6 Postoperative follow-up sigmoidoscopy of the rectal stump at 3 months and 12 months after surgery. A: At 3 months after surgery, the rectal stump showed mild erythema and friability without definite ulceration; B: At 12 months after surgery, the rectal stump demonstrated recurrent mucosal inflammation with erythema, friability, and newly developed shallow ulcerations. These findings indicate interval worsening of rectal inflammation over time.

DISCUSSION

IMHMV is a rare, non-thrombotic, non-inflammatory venous occlusive disease that causes chronic intestinal ischemia and frequently mimics IBD, particularly UC. Since its first description in 1991, accumulated reviews have shown that IMHMV remains a diagnostic challenge despite increasing recognition[1,8]. Recent literature reviews summarizing more than 80 reported cases indicate that more than half of patients were initially diagnosed with IBD before surgery, underscoring the substantial clinical overlap between IMHMV and UC[8,9]. Abdominal pain, diarrhea, hematochezia, and weight loss are common presenting symptoms, and endoscopic findings may show erythema, edema, friability, erosions, ulceration, or continuous colitis, all of which can resemble UC or ischemic colitis[2-4,8,10]. Similar diagnostic pitfalls are well recognized in ischemic colitis and other mesenteric vascular disorders, where nonspecific symptoms and overlapping endoscopic findings can delay accurate diagnosis[11,12]. Table 1 summarizes the distinguishing clinical, endoscopic, and histopathologic features of IMHMV and its major differential diagnoses, which may facilitate earlier recognition of this rare entity.

Table 1 Differential diagnosis of idiopathic myointimal hyperplasia of mesenteric veins and other causes of inflammatory colitis.

Disease	Clinical features	Endoscopic findings	Histopathology	Distinguishing features
IMHMV	Chronic bloody diarrhea, left-sided predominance, steroid-refractory	Segmental erythema, deep ulcers, edema	Myointimal hyperplasia of mesenteric veins with preserved arteries	Diagnosis usually requires surgical specimen
Ulcerative colitis	Chronic relapsing bloody diarrhea	Continuous inflammation from rectum	Chronic active colitis, crypt distortion	Responds to immunosuppressive therapy
CMV colitis	Immunocompromised host	Large punched-out ulcers	CMV inclusion bodies	CMV IHC/PCR positive
MMF-induced colitis	MMF exposure	Variable erythema/ulcers	Increased epithelial apoptosis	Improves after MMF withdrawal
Infectious colitis	Acute onset, fever	Diffuse erythema, exudate	Acute neutrophilic inflammation	Positive stool studies
Ischemic colitis	Acute abdominal pain	Segmental ischemic ulceration	Ischemic injury	Typical vascular risk factors
Enterocolic lymphocytic phlebitis	Abdominal pain and diarrhea; may mimic IBD or ischemic colitis	Segmental or diffuse inflammatory/ischemic changes	Lymphocytic inflammation selectively involving veins and venules, with arterial sparing	True venous phlebitis with lymphocytic infiltration, unlike non-inflammatory myointimal hyperplasia in IMHMV

IMHMV: Idiopathic myointimal hyperplasia of mesenteric veins; CMV: Cytomegalovirus; IHC: Immunohistochemistry; PCR: Polymerase chain reaction; MMF: Mycophenolate mofetil; IBD: Inflammatory bowel disease.

Histopathologically, IMHMV is characterized by marked myointimal hyperplasia of mesenteric veins, luminal narrowing or obliteration, subendothelial fibrin deposition, capillary arteriolization, and preservation of adjacent arterial structures[1,2]. These findings reflect a structural venous outflow disorder rather than primary inflammatory vasculitis or thrombotic vascular occlusion. Routine mucosal biopsies are often nondiagnostic because the characteristic abnormalities mainly involve submucosal or mesenteric veins, and superficial biopsies may show only nonspecific chronic or ischemic-type inflammation[2-4,6,8]. However, mucosal biopsies are not always uninformative; reported clues include arteriolized capillaries, subendothelial fibrin deposition, and perivascular hyalinization when deeper or diagnostically relevant vessels are sampled[6,7,13]. In the present case, initial biopsies showed only nonspecific chronic inflammation, whereas the resected specimen demonstrated near-complete venous luminal obliteration, subendothelial fibrin deposition, and arterial sparing without vasculitis or thrombotic occlusion, confirming IMHMV.

The clinical course of this patient highlights the limitations of medical therapy when IMHMV is misdiagnosed as UC. Under the presumptive diagnosis of steroid-refractory UC, the patient was treated with mesalazine, corticosteroids, and filgotinib, a selective Janus kinase 1 inhibitor. Filgotinib was selected after consultation with IBD experts because the diagnosis of UC was not considered definitive and the anticipated benefit-risk profile was carefully weighed in view of the patient’s advanced age, history of liver transplantation, and ongoing immunosuppression. Nevertheless, progressive clinical deterioration culminated in massive hematochezia requiring emergency surgery. In retrospect, because IMHMV is a structural venous occlusive disorder rather than an immune-mediated inflammatory disease, switching to an alternative Janus kinase inhibitor would not have been expected to modify the underlying disease process. This is consistent with prior reviews showing that IMHMV responds poorly to conventional IBD therapy and is usually treated surgically[3,4,8]. A systematic review of surgical management reported that nearly all patients underwent surgery, with postoperative remission achieved in almost all cases, whereas preoperative suspicion of IMHMV remained uncommon[9]. Unlike thrombotic mesenteric venous occlusion, such as portal or superior mesenteric vein thrombosis, which may respond to anticoagulation, thrombolysis, or endovascular intervention, IMHMV represents an irreversible structural venous lesion caused by myointimal hyperplasia[14]. Therefore, surgical resection remains the definitive treatment.

Radiologic findings can provide useful clues but are not diagnostic. Conventional CT findings of IMHMV include diffuse colonic wall thickening, submucosal edema, and pericolonic fat stranding, which substantially overlap with UC and other colitides[4,8,12,15]. More specific vascular clues have been described, including engorged or ectatic mesenteric/pericolic veins, impaired visualization of the inferior mesenteric vein, cord-like inferior mesenteric vein appearance, and early venous enhancement on CT angiography, suggesting venous outflow disturbance[15-17]. Similar venous congestion-related colitis may occur in other vascular disorders of the left colon, such as inferior mesenteric arteriovenous fistula[16]. In our patient, CT demonstrated diffuse wall thickening and pericolonic fat stranding, initially interpreted as compatible with UC. In retrospect, the venous ischemic nature of IMHMV emphasizes the need to evaluate mesenteric venous drainage carefully when colitis appears refractory or disproportionate to biopsy findings.

An additional diagnostic issue in this case was the postoperative course. After resection of the affected colon, inflammation recurred in the rectal stump, and biopsy showed chronic colitis with cryptitis, lymphoplasmacytic infiltration, glandular distortion, and mucin depletion. Symptoms improved after topical mesalazine therapy. These findings raised the possibility of a coexisting UC component; however, this interpretation requires caution. Diversion colitis is common in defunctionalized bowel segments and may show chronic active colitis-like features, including crypt distortion and mucin depletion, thereby mimicking IBD histologically[18,19]. Rectal stump inflammation after subtotal colectomy is also frequent in UC patients, and a cohort study reported high rates of active rectal stump inflammation and diversion colitis[20]. Moreover, response to topical 5-aminosalicylic acid or corticosteroid therapy does not exclude diversion colitis, as several reports and reviews have described improvement of diversion colitis with topical anti-inflammatory therapy[21-23].

Therefore, the postoperative rectal stump inflammation in this case should not be interpreted as definitive proof of UC. Rather, the most balanced interpretation is that IMHMV was the dominant driver of the initial severe colitis and surgical deterioration, while a coexisting UC component remains possible but unproven. One plausible hypothesis is that venous ischemic injury initially dominated the clinical picture and obscured an underlying inflammatory phenotype, which later became apparent in the residual rectum after removal of the ischemic segment. A similar diagnostic scenario, in which UC emerged on a background of diversion-related inflammation, has been reported, supporting the plausibility of this interpretation while not proving causality in the present case[24]. Thus, differentiation among coexisting UC, diversion colitis, and other causes of postoperative rectal inflammation cannot be conclusively established from a single case.

This case has several clinically important implications. First, IMHMV should be considered in patients with steroid-refractory colitis, particularly when mucosal biopsies are nonspecific or discordant with disease severity. In solid organ transplant recipients, diarrhea and colitis have a broad differential diagnosis, including opportunistic infections (particularly cytomegalovirus infection), medication-related injury, ischemic colitis, and de novo IBD[25,26]. Mycophenolate mofetil-induced colitis is particularly relevant because both its endoscopic and histologic findings may closely mimic IBD or ischemic colitis[27]. De novo IBD, although uncommon, may also develop after solid organ transplantation despite ongoing antirejection immunosuppressive therapy, and appears to be reported more frequently after liver transplantation than after transplantation of other solid organs[25,26]. Therefore, infectious and medication-related etiologies should be carefully excluded before establishing a diagnosis of de novo IBD in a transplant recipient[26,27]. No established association between IMHMV and solid organ transplantation or immunosuppression itself has been described. Rather, the present case illustrates that IMHMV should also be considered when biopsy findings are nonspecific and the clinical course remains refractory to appropriate medical therapy. Second, careful review of biopsy specimens for subtle vascular clues may occasionally raise preoperative suspicion, although definitive diagnosis still often depends on resection pathology. Third, imaging should not be limited to mucosal inflammation but should include careful assessment of mesenteric venous drainage, particularly in left-sided refractory colitis. Finally, postoperative endoscopic and histologic follow-up is important when residual rectal inflammation persists or recurs, because IMHMV alone, diversion colitis, and coexisting IBD may require different long-term management strategies.

CONCLUSION

In conclusion, IMHMV is an important mimicker of UC and should be included in the differential diagnosis of steroid-refractory colitis with nonspecific biopsy findings. This case is notable for its occurrence in a liver transplant recipient, fulminant deterioration despite IBD-directed therapy, definitive diagnosis by surgical pathology, and postoperative rectal stump inflammation responsive to topical mesalazine. The latter finding suggests a possible coexisting UC component, but diversion colitis remains an important competing explanation. Accurate diagnosis requires integration of clinical course, endoscopic pattern, imaging findings, histopathology, and longitudinal postoperative follow-up. Misinterpretation of such postoperative findings may lead to inappropriate re-initiation of systemic immunosuppression.