32 Abdominal Pain in Crohn’s Disease: When it Isn’t Just a Flare

Background: Abdominal and pelvic pain are common presenting complaints in patients with Inflammatory Bowel Disease (IBD). While disease flares are often suspected, it is essential to maintain a broad differential diagnosis. Over-attribution of symptoms to IBD can delay recognition of other important conditions, particularly in patients with complex surgical histories and overlapping inflammatory disorders. Nutcracker syndrome, a rare vascular compression disorder caused by left renal vein entrapment between the superior mesenteric artery and aorta, has not been widely reported in patients with IBD. Methods: We present a 31-year-old female with penetrating Crohn’s colitis complicated by perianal and pouch fistulas, cutaneous Crohn’s disease, pelvic sepsis, hidradenitis suppurativa and sacral osteomyelitis. Her extensive surgical history included colectomy with ileal pouch–anal anastomosis, pouch excision with end ileostomy, sacrectomy, multiple examinations under anesthesia, and soft tissue reconstruction. She had previously been exposed to infliximab and adalimumab but discontinued secondary to side effects and was transitioned to risankizumab. Despite this regimen, she presented on multiple occasions with nausea, abdominal pain, and concerns for Crohn’s flare, though prior assessments repeatedly showed no evidence of active luminal inflammation. Results: On this admission, her C-reactive protein was 1.5 mg/dL, notably lower than her baseline of 3 mg/dL, and fecal calprotectin was 8.7 μg/g. CT imaging demonstrated no active intestinal inflammation but revealed a soft tissue density involving the vagina, perineal region, and gluteal subcutaneous fat with small locules of internal air suggestive of a prior fistula. The scan also identified focal narrowing of the left renal vein between the aorta and superior mesenteric artery with associated venous collaterals. Abdominal Doppler ultrasound further confirmed increased velocity in the left renal vein distal to the superior mesenteric artery crossing, consistent with vascular narrowing and suggestive of nutcracker syndrome. Conclusions: This case underscores the importance of maintaining a broad differential diagnosis when evaluating abdominal and pelvic pain in patients with IBD. Not all symptoms are attributable to a disease flare, particularly in individuals with complex surgical and comorbidity profiles. Nutcracker syndrome, though rare, should be considered when imaging suggests vascular compression. Awareness of this vascular anomaly may help avoid unnecessary escalation of IBD therapy and guide more targeted management strategies.