Perforated sigmoid colon diverticulitis initially presenting with pneumoperitoneum, pneumoretroperitoneum, and pneumomediastinum: A case report

Abstract

BACKGROUND

Complications occur in approximately 12% of cases of diverticulitis, with perforation occurring in up to 10% of complications. Typically, patient with perforated diverticulitis present intraperitoneally with abdominal pain and peritoneal signs. By contrast, pneumoretroperitoneum and pneumomediastinum are rare complications and lack typical symptoms, making their diagnosis difficult and often delayed, leading to increased morbidity and mortality.

CASE SUMMARY

A 66-year-old man presented with lower abdominal pain for 3 days. On examination, his vital signs were stable, and the abdomen was soft with mild distension and left lower quadrant tenderness, but no peritoneal signs were noted. Laboratory tests indicated leukocytosis and a markedly elevated C-reactive protein level. Abdominal computed tomography (CT) revealed focal wall thickening and fat stranding near the rectosigmoid junction as well as pneumoretroperitoneum, pneumomediastinum, and minor pneumoperitoneum. Suspecting hollow organ perforation, an emergent exploratory laparotomy was performed which revealed a retroperitoneal abscess with mesocolonic necrosis, likely due to perforated sigmoid diverticulitis. The patient underwent sigmoid resection with Hartmann’s procedure and retroperitoneal drainage. Follow-up CT on postoperative day 14 confirmed resolution of the free air, and the patient was discharged on postoperative day 40 with an uneventful recovery.

CONCLUSION

Pneumoretroperitoneum and pneumomediastinum are rare complications of perforated diverticulitis, often with delayed diagnosis due to the absence of peritoneal signs. CT aids detection, and timely surgical intervention is crucial.

Key Words: Diverticulitis; Colonic perforation; Pneumoperitoneum; Pneumoretroperitoneum; Pneumomediastinum; Case report

Core Tip: This case highlights the rare but critical complications of pneumoretroperitoneum and pneumomediastinum in perforated diverticulitis, emphasizing the importance of high clinical suspicion in patients with atypical presentations. Timely computed tomography imaging and prompt surgical intervention are essential, as delayed diagnosis can lead to increased morbidity and mortality. Despite the absence of typical peritoneal signs, early detection and intervention are crucial for improving patient outcomes.

INTRODUCTION

Complications occur in approximately 12% of cases of diverticulitis[1]. Common complications include abscesses (69%), peritonitis (27%), obstruction (15%), and fistulas (14%)[1]. In patients with acute diverticulitis, the rate of perforation can reach 10%[2]. In the majority of cases, the perforation occurs intraperitoneally, and the patient may present with acute abdominal pain, nausea, and vomiting. Hemodynamic instability accompanied by hypotension and shock may occur in severe cases. Physical examination may reveal peritoneal signs with abdominal guarding, rigidity, and rebound tenderness. Unlike intraperitoneal perforation, pneumoretroperitoneum is a relatively rare complication of perforated diverticulitis. Because of the lack of typical symptoms, diagnosing retroperitoneal colon perforation can be challenging. Moreover, delayed diagnosis and treatment are associated with high morbidity and mortality rates[3]. According to the World Society of Emergency Surgery (WSES) guidelines, uncomplicated diverticulitis may be managed conservatively, whereas complicated diverticulitis, such as cases with perforation, typically requires urgent surgical or interventional management[4]. Herein, we present a rare case of a 66-year-old man who exhibited no toxic signs but received a diagnosis, after clinical workup, of perforated sigmoid diverticulitis that resulted in pneumoperitoneum, pneumoretroperitoneum, and even pneumomediastinum.

CASE PRESENTATION

Chief complaints

A 66-year-old man presented to the Emergency Department with a chief complaint of lower abdominal pain for the preceding 3 days.

History of present illness

The patient had experienced dull, intermittent lower abdominal pain for 3 days without any exacerbating or relieving factors. Nausea and poor appetite were also mentioned. He had a vomiting episode on the day he sought medical treatment.

History of past illness

The patient had history of hypertension and chronic obstructive pulmonary disease with medication control.

Personal and family history

The patient had a 30-year history of smoking one pack per day but had quit smoking 5 years previously. He had no significant occupational or social issues, and no major contributory diseases or genetic disorders in the family had been recorded.

Physical examination

Physical examination revealed a soft and mildly distended abdomen. Mild tenderness was observed in the left lower quadrant with deep compression. Neither abdominal guarding nor rebounding pain suggesting peritoneal involvement was observed.

Laboratory examinations

Laboratory tests revealed a white blood cell count of 18720 /μL, a neutrophil level of 91%, a hemoglobin level of 9.2 g/dL, a creatinine level of 1.75 mg/dL, and a C-reactive protein level of 403.19 mg/dL; other parameters were within normal limits.

Imaging examinations

Abdominal computed tomography (CT) was performed with intravenous contrast. Axial, sagittal and coronal reconstructions were obtained. The CT examination revealed mural changes including focal wall thickening and edematous changes at the rectosigmoid junction. The extramural findings were peripheral fat stranding around the affected segment, diffuse pneumoretroperitoneum around the pancreas and kidneys, minor pneumoperitoneum, and pneumomediastinum (Figure 1).

Figure 1 Selected images from non-enhanced computer tomography of the abdomen. A: Perforation of the sigmoid colon (arrow); B: Pneumoretroperitoneum around pancreas and kidney (arrow); C: A lung window setting demonstrating pneumomediastinum (arrow); D: Computer tomography scan sagittal view showing pneumomediastinum, pneumoperitoneum, and pneumoretroperitoneum (arrows).

FINAL DIAGNOSIS

Perforated sigmoid colon diverticulitis with pneumoperitoneum, pneumoretroperitoneum, and pneumomediastinum. The CT findings indicated that the case corresponded to Hinchey stage II and was most consistent with WSES stage 2B complicated diverticulitis.

TREATMENT

Because intra-abdominal infection caused by hollow organ perforation was suspected, an exploratory laparotomy was arranged immediately. During the procedure, the abdominal cavity was confirmed to be clean without contaminated ascites. However, mild necrosis and an unpleasant odor were identified in the mesocolon tissue near the sacral promontory. After blunt and sharp dissection of necrotic tissue, a retroperitoneal space abscess with tissue necrosis was observed, which was suspected to have been induced by sigmoid colon diverticulitis perforation in the mesenteric area (Figure 2). Therefore, sigmoid colon resection and Hartmann reconstruction were conducted. Further blunt dissection of the retroperitoneal space was performed gently through a finger-based approach. Drainage tubes were then placed in the retroperitoneal space and in the rectovesical pouch.

Figure 2 Intra-operative picture. A: Sigmoid colon diverticulitis with necrotic change (arrow); B: Retroperitoneal space abscess formation, favor mesenteric site diverticulitis perforation related (arrow); C: Blunt dissection of retroperitoneal space performed with finger (arrow).

OUTCOME AND FOLLOW-UP

As empirical therapy for sepsis, intravenous piperacillin-tazobactam (4.5 g every 8 hours) was administered for 2 weeks following the operation, along with fluid hydration. Following hospitalization in the intensive care unit for 5 days, the patient was transferred to a general ward. In the general ward, intermittent low-grade fever was observed, which was suspected to be an acute complication of chronic obstructive pulmonary disease. Abdominal CT on postoperative day 14 revealed no free air in the retroperitoneal space or mediastinum. The patient was discharged on postoperative day 40. His pathology report revealed acute peritonitis and subserosal necrosis, compatible with our intraoperative findings.

DISCUSSION

Pneumoretroperitoneum can result from perforation of the duodenum or posterior aspects of the ascending, descending, and sigmoid colon segments. Patients with pneumoretroperitoneum may present with no clinical signs, which delays their diagnosis and increases the risk of life-threatening complications[3]. Free air in the retroperitoneum may travel through anatomical fascial planes into the esophageal or aortic hiatus of the diaphragm and to the mediastinum[5,6]. The visceral space, as described by Maunder et al[5], is a soft tissue compartment with a fascial plane that connects cervical soft tissues with the mediastinum and retroperitoneum, allowing air leakage. Our patient presented with major emphysema spanning from the mesentery to the retroperitoneum and mediastinum. Multiple cases of sigmoid colon perforation accompanied by pneumoretroperitoneum and pneumomediastinum have been reported in the literature[7-9]. A literature review of 20 cases of pneumomediastinum following colonic perforation, with cases of iatrogenic and traumatic injury excluded, revealed that all cases involved perforation in the retroperitoneal or intramesenteric space. The most common cause of pneumomediastinum of colonic origin was found to be diverticulitis (13 cases), primarily in the sigmoid colon (12 cases)[7].

Diagnosing perforated diverticulitis in patients with atypical symptoms can be challenging. Therefore, diagnosis can often be delayed, particularly in the absence of peritoneal signs and abdominal pain associated with intramesenteric perforation. Many patients in whom diagnosis are delayed have an autoimmune disease and are prescribed either a steroid or immunosuppressive agent, which typically masks the symptoms of diverticulitis perforation. Even if no peritoneal irritation is noted in the majority of cases, fever or unstable vital signs, such as hypotension or shortness of breath, are commonly observed. Our patient presented with no peritoneal signs and with stable vital signs. CT was arranged because of the high suspicion of infection. In stable patients, CT remains the gold standard for diagnosing diverticulitis because it enables visualization of findings such as colonic wall thickening, pericolic fat stranding, abscesses, free air, and perforation, and these findings directly inform disease classification in the WSES 2020 guidelines and can guide appropriate management[4]. In the detection of free air, CT has a success rate of approximately 85%[3,9]. In certain cases, free air may travel to other areas as a result of the pressure gradient, causing subcutaneous emphysema, pneumopericardium, or pneumothorax[6-8,10,11]. This phenomenon of free air travel may be attributed to the relatively long interval between symptom onset and the initiation of therapy, and it can be clearly observed on CT or radiography scans. Bormann et al[8] reported a rare case of a patient who presented with hoarseness due to subcutaneous emphysema caused by perforated diverticulitis. In summary, patients presenting with subcutaneous neck emphysema without a thoracic etiology must undergo further assessment for gastrointestinal sources.

Prompt surgical treatment is required when perforated diverticulitis is suspected. According to the 2020 update of the WSES guidelines, whether a case of acute colonic diverticulitis is of the uncomplicated or complicated form must be determined because the appropriate management strategies for these forms differ substantially. Uncomplicated diverticulitis can often be managed conservatively, whereas complicated diverticulitis includes conditions such as abscess, perforation, obstruction, and fistula formation, which usually require surgical or interventional treatment. Further subclassification of complicated diverticulitis into diverticulitis with vascular (e.g., bleeding, ischemia) or nonvascular (e.g., perforation, abscess, obstruction, fistula) complications may provide a more comprehensive framework for clinical evaluation and tailored management strategies[4]. In the reported cases, almost all patients underwent Hartmann’s procedure. After surgery, most of them survived, with only two deaths reported. Each patient was hospitalized for a duration depending on their disease severity and concurrent comorbidities[7-9]. Several randomized controlled trials have compared Hartmann’s procedure with resection accompanied by primary anastomosis with or without a diverting stoma in patients with Hinchey III-IV diverticulitis[12,13]. However, none of these trials mentioned diverticulitis perforation in the retroperitoneal space. In addition to resection of the diseased segment of the colon and performance of proximal diverting colostomy, opening of the retroperitoneal space for abscess drainage and irrigation is necessary. Notably, pneumoperitoneum and pneumomediastinum in this setting do not require specific intervention. Once the perforation source has been controlled surgically, free air in the peritoneum, retroperitoneum, and mediastinum is gradually reabsorbed. This explains why postoperative follow-up CT in our patient revealed spontaneous resolution of the free air. Patients with pneumoretroperitoneum and pneumomediastinum require tailored management strategies depending on the source of free air and their clinical state.

CONCLUSION

Pneumoretroperitoneum and pneumomediastinum are rare but serious complications of perforated diverticulitis. Their diagnosis may be delayed, particularly when the patient exhibits no peritoneal signs. Laboratory examinations and CT may be useful. Prompt surgical intervention, such as laparotomy, should be considered in cases of perforated diverticulitis.