Case Presentation: A 55-year-old female with a history of metastatic left renal cell carcinoma to the left hemipelvis status post nephrectomy and immunotherapy, and generalized anxiety disorder presented for chronic diarrhea described as over 10 episodes of large volume watery stools daily persisting with fasting and associated with cramping abdominal pain. She reported that previous treatments including loperamide, steroids, and courses of oral vancomycin and fidaxomicin for presumed Clostridium difficile colitis were ineffective. On initial presentation, her vital signs and physical examination were unremarkable, except for dry mucous membranes and diffuse abdominal tenderness. Initial lab values were notable for potassium of 2.1 mMol/L, bicarbonate of 17 mMol/L, BUN of 25 mg/dL, creatinine of 1.6 mg/dL, and magnesium of 0.6 mMol/L. Diagnostic results spanning the course of multiple hospitalizations over the past three months, including antinuclear antibody, celiac panel, calcitonin, vasoactive intestinal polypeptide, giardia antigen, Clostridium difficile GDH and toxin tests, Shiga toxin, ova and parasites, stool and blood cultures, and multiple CT abdomen/pelvis studies, were unremarkable. Gastric and duodenal biopsies revealed mild chronic gastritis with no evidence of helicobacter organisms and intraepithelial lymphocytosis with mild villous alteration, respectively; terminal ileum biopsy reported no villous atrophy or enteritis. A 24-hour urine 5-hydroxyindoleacetic acid (17.8 mg/24-hour), Chromogranin A (945 ng/mL), and gastrin (285 pg/mL) levels were elevated. The patient was discharged with referral for octreotide scintigraphy but was lost to follow-up.
Discussion: Optimal strategies for evaluating chronic diarrhea have not been well established, although a specific diagnosis is achievable in over 90 percent of cases [1]. Our case highlights a challenging diagnostic journey involving refractory chronic diarrhea, where extensive evaluations and multiple hospital admissions failed to identify the underlying cause and further necessitates the importance of considering carcinoid syndrome in the differential diagnosis of persistent, unexplained gastrointestinal symptoms, even when other malignancies are present. Moreover, chronic diarrhea imposes a substantial economic burden due to its prevalence and the significant resources required for management with costs estimated to exceed millions of US dollars annually [2]. Considering rare but impactful conditions like carcinoid syndrome can enhance diagnostic accuracy and treatment efficacy, thereby benefiting both patients by alleviating symptoms more swiftly and healthcare by utilizing resources more efficiently.
Conclusions: Chronic diarrhea, characterized by persistent loose stools for over four weeks, has diverse causes and significantly impacts healthcare costs and productivity due to extensive diagnostic and management needs. Among its rarer causes, carcinoid syndrome from neuroendocrine tumors presents a unique diagnostic challenge. Early recognition of such rare conditions is crucial for effective management, highlighting the importance of timely diagnosis in chronic diarrhea cases.
