Case Presentation: A 50-year-old male presented to the emergency room with worsening left lower quadrant abdominal pain of two days duration associated with subjective fever and diarrhea. Three weeks prior to his presentation, he was diagnosed with acute diverticulitis confirmed by abdominal CT scan and completed a seven-day course of Ciprofloxacin and Metronidazole. Physical exam revealed a temperature of 36.4C, pulse 136/min, BP of 140/85, tenderness in the left lower quadrant without any peritoneal signs. Blood work showed no leukocytosis and a repeat CT of the abdomen showed worsening sigmoid diverticulitis with new septic thrombophlebitis of the Inferior Mesenteric vein extending to the Porto splenic confluence [Image 2]. Patient was admitted, placed on bowel rest, treated with intravenous Piperacillin/Tazobactam, fluids, Heparin drip and oral Vancomycin as his stool for C. diff toxin gene by PCR was positive. His blood cultures were negative and flow cytometry showed no evidence for a lymphoproliferative or myeloproliferative disorder. Due to persistent abdominal pain, he underwent hemicolectomy and a coloproctostomy. Pathology of colon showed acute diverticulitis with peri colonic abscess. The patient was discharged home and advised to complete the remaining 14 days of oral Vancomycin and six-month course of Coumadin.

Discussion: Clinical cases of Inferior Mesenteric Vein thrombosis (IMV) complicating acute diverticulitis is rare and comprises of 4-11% of cases but carries a 15-23% risk of mortality. Acute diverticulitis can cause inflammation of IMV by peri colonic abscess and thrombosis occurs by inflammatory mediators causing endothelial injury and activation of coagulation cascade. Sigmoid diverticulitis is the most common causative etiology of thrombophlebitis of IMV accounting for 30% of cases, the remaining other causes are appendicitis (19%), IBD (6%), pancreatitis (5%), infectious enteritis (4%), bowel perforation and malignancies (6%) [1]. There is high mortality in cases complicated by hepatic abscess or bowel ischemia. The clinical presentation of septic thrombophlebitis of IMV is insidious with vague symptoms delaying early diagnosis and therefore requires a high index of suspicion. CT scan of the abdomen with contrast is generally the first test of choice with direct visualization of endoluminal thrombus [1]. Bacteremia is typically polymicrobial with E. Coli, Bacteroides, Streptococcus Viridians, Proteus Mirabilis and Klebsiella Pneumonia being the most common pathogens [2]. Sterile blood cultures in our patient can be explained by the prior use of antibiotics. Treatment with broad spectrum antibiotics and systemic anticoagulation often has a favorable outcome when compared to treatment with antibiotics alone [2]. The use of modern diagnostic imaging and broad-spectrum antibiotics have lowered mortality rate from pylephlebitis to approximately 25% as observed in reports published after 1990 when compared to 77% before 1990 [1,2].

Conclusions: This case illustrates the fact that IMV thrombosis though a rare complication of acute diverticulitis requires a high index of suspicion for a prompt diagnosis and to prevent complications.
1. Anna L. Falkowski, Gieri Cathomas, et al. Pylephlebitis of a variant mesenteric vein complicating sigmoid diverticulitis. J Radiol Case. 2014 Feb; 8(2):37-45
2.Kanellopoulou T, Alexopoulou A, et al. Scand. Pylephlebitis: an overview of non-cirrhotic cases and factors related to outcome J Infect Dis. 2010;42(11–12):804–11.

IMAGE 1: Image 1: Comparison of CT images: Image A is an initial CT scan with an arrow pointing to the Inferior Mesenteric Vein (IMV) with no thrombus and Image B is a repeat CT scan three weeks later with an arrow pointing to the IMV which has a low attenuation clot

IMAGE 2: Image 2: Image A is the sagittal section displaying an arrow pointing at sigmoid diverticulits and Image B is a coronal section displaying an arrow pointing at the confluence point of Superior Mesenteric Vein and Inferior Mesenteric Vein with thrombus.