GS01 - A Case of Idiopathic Myointimal Hyperplasia of the Mesenteric Veins: A Rare Cause of Chronic Ischemic Colitis

Introduction/Purpose: Colonic ischemia presents in a variety of forms with a myriad of causative factors. The primary mechanism underlying ischemic colitis is insufficient blood supply to the colon to sustain the cellular processes required for metabolism, with the potential to result in mucosal necrosis. Patient presentation, approach to diagnostics, and modalities of treatment can be broadly organized by whether the ischemic insult occurs over an acute or chronic time course. Within this case report, we will focus on idiopathic myointimal hyperplasia of the mesenteric veins, a lesser-known cause of chronic mesenteric ischemia. This condition is characterized by proliferation of the myointimal layer of small and medium-sized mesenteric veins, resembling the venous arterialization that may be seen in arteriovenous fistulae and saphenous vein grafts utilized in cardiac bypass surgery.^[1] Patients may experience symptoms consistent with inflammatory bowel disease (IBD) such as abdominal pain, bloating, diarrhea, compromised nutritional status, etc.^[7] Their symptoms may be refractory to medical therapy and their presentation can have endoscopic and other clinical features consistent with IBD. IMHMV is an exceedingly rare cause of chronic ischemic colitis and may be confused for a host of other pathologies. Since it was first described by Genta and Haggitt in 1991, only nine cases have been reported. ^[4] This low number likely represents underreporting of actual cases given its resemblance to other disease processes.

We present a case of IMHMV in a 63-year-old Caucasian male who presented to our Emergency Department with abdominal pain and fecal urgency and frequency, impairing his quality of life. The patient had a history of these symptoms periodically throughout the months but without a diagnosis nor treatment that provided long-lasting relief of symptoms. During his hospitalization, he received CT imaging, underwent colonoscopy, and was treated with oral and rectal mesalamine and IV methylprednisolone, without significant reduction in his symptoms. Because he was refractory to medical management, he ultimately underwent a laparoscopic converted to open left hemicolectomy with low anterior resection, biopsies demonstrating ischemic colitis. Pathology from specimen resected during the case demonstrated IMHMV.

Methods or Case Description: A 63-year-old Caucasian male, retired from military service presented to the emergency department with complaints of increasing frequency of gastrointestinal cramping, left lower quadrant abdominal pain, increasing frequency and associated urgency with bowel movements, and passing mucous and small “flake-like” stools. He reported a pertinent past medical history of 2 episodes of uncomplicated diverticulitis treated with oral antibiotics two to three years prior, and colonoscopy approximately three years before presentation. At the time, the colonoscopy demonstrated only diverticulosis. His surgical history included ocular procedures, orthopedic procedures, and a hemorrhoidectomy a few years prior to presentation. Ciprofloxacin, augmentin and flagyl were successfully used in the past to suppress the acute symptoms, but he reported ongoing intermittent smoldering pain and fecal urgency. His symptoms had slowly been increasing in severity, and he reported a 17-pound weight loss over the prior 3 months despite dietary modifications as an attempt to ameliorate his symptoms. His quality of life was severely impaired by his frequent need to defecate and ongoing discomfort. Physical exam revealed mild tenderness to palpation in the left lower quadrant, with moderate tenderness in the mid suprapubic region. A mass could be palpated with heterogeneous firmness tracking along the left lower quadrant. No peritonitic signs were elicited. Laboratory evaluations were significant for mild anemia with a hemoglobin of 11.4 g/dL. No leukocytosis, electrolyte abnormalities, or concerning acid-base findings were detected. Urinalysis revealed only proteinuria. CT abdomen/pelvis with contrast was obtained which showed diffuse wall thickening of the descending and sigmoid colon and the rectum, with extensive edema and adjacent inflammation. The imaging was noted to be similar in character to prior CT imaging, consistent with colitis. The patient was admitted for expeditious workup to include colonoscopy. He was started on intravenous fluids, antibiotics including ciprofloxacin and flagyl and was scheduled for a gastroenterology consult for colonoscopy the following day.

At this stage, differential diagnosis included diverticulitis, inflammatory bowel disease, infectious colitis, malignancy, segmental colitis associated with diverticulosis (SCAD), and ischemic colitis. Given his multiple courses of broad-spectrum antibiotics, there was concern for Clostridium difficile (C. diff) infection, but a stool sample was polymerase chain reaction (PCR) negative for this pathogen. Ova and parasite testing from a stool sample was also negative. The patient was prepped for and underwent colonoscopy with gastroenterology. Colonoscopy revealed severe, Mayo 3 left-sided colitis.

Previously seen diverticulosis was visualized throughout the entire colon, but most severe within the descending and sigmoid colon. Circumferential edematous, erythematous, and ulcerated purplish mucosa was seen extending continuously from the distal descending colon to rectosigmoid junction. Rectal mucosa was mildly edematous and had loss of vascularity, but no ulceration. Terminal ileum, ascending and transverse colon were all normal. Elastin stain of mesenteric vessels demonstrated a markedly thickened mesenteric vein (Figure 1). H&E stain demonstrated loss of surface epithelium with preservation of crypts, increased inflammation of the lamina propria, and prominent smell vessels within fibrin thrombi (Figure 2).

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Outcomes: Following initial surgery, the patient underwent Hartmann’s procedure, which was reversed. The patient required a diverting loop ileostomy due to technically challenging and extended reversal surgery. The patient is currently pending ileostomy reversal in July 2022. Otherwise, the patient is progressing well, with no reoccurrence of initial complaints.

Conclusion: We present a case of IMHMV in a 63-year-old retired military service member with a history of diverticulitis. In this case, the patient’s complaints of gastrointestinal cramping, left lower quadrant abdominal pain, increasing frequency and associated urgency with bowel movements, and passing mucous and small “flake-like” stools were refractory to typical antibiotic and medical treatment. Initial evaluation considered a diagnosis of IBD; however, due to the failure of the patient’s ailments to respond to antibiotics and his declining quality of life, the patient underwent an extensive work up, including the usage of colonoscopy.

Colonic ischemia, the most common form of gastrointestinal ischemia, is the result of insufficient blood supply to meet colonic demand, oftentimes a result of inadequate blood supply near Griffith’s point, the point where blood from the superior mesenteric artery and the inferior mesenteric artery meet. ^{[3, 5]} In contrast to the typical etiology of ischemic colitis, our patient presented with the rare finding of colonic ischemia due to idiopathic myointimal hyperplasia of the mesenteric veins. Originally reported in 1991, IMHMV is a rare and poorly understood condition with as few as nine cases reported in the literature. ^{[6, 2]} It most commonly occurs in patients in their 30s in the rectosigmoid area. ^[2] Additionally, IMHMV is oftentimes associated with vasculitis or autoimmune disease. Contrastingly, our patient was an elderly man with no history of autoimmune disease or vasculitis.

Because IMHMV follows a similar clinical presentation to IBD, biopsies are necessary to rule out other inflammatory bowel diseases, rendering a diagnosis of IMHMV to be less frequent. Patients presenting with symptoms similar to irritable bowel disease with recent weight loss should raise suspicion for a diagnosis of IMHMV. Additional research should target the etiology and pathophysiology of IMHMV and its association with ischemic colitis.