Acute Tubular Necrosis as a Complication of Collagenous Colitis

Abstract

Introduction: Microscopic colitis is a subdiagnosed cause of chronic diarrhea, especially among the elderly, although it can occur in patients of any age. This case evidences the potential seriousness of the pathology, in particular, the development of acute tubular necrosis which could be prevented by an early diagnosis. Case Report: An 80-year-old man, previously healthy, with a history of watery diarrhea, anorexia occasional abdominal cramps and weight loss (9 kg), in the last 5 months. He was submitted to a colonoscopy 1 month before, which did not showed endoscopic lesions, and treated with loperamide, but without improvement. There was no history of joint pains or swelling, fever or use of non-steroidal antiinflammatory drugs. He recurred to the emergency department due to worsening diarrhea, asthenia and dizziness. On the physical exam he was pale and dehydrated. Laboratory tests showed iron deficiency anemia, acute tubular necrosis (creatinine of 12.8mg/dL, eGFR of 4ml/min (1.73m2) and hypokalemia (K+ 2.4mEq/L). Urinary tract infection and obstruction were excluded and he was admitted on an intensive care unit. Stool cultures were negative, including specific tests forbacteria or parasites. The presence of celiac disease was excluded with normal duodenal biopsies and negative serologic testing. An ileocolonoscopy was performed, revealing a mucosa with normal appearance. Biopsies of the right and left colon were taken and the histopathological exam was consistent with the diagnosis of collagenous colitis. He presented progressive improvement of the renal impairment, with fluids and correction of the hydroelectrolytic disorders, without the need of haemodialysis. The patient was treated with oral budesonide with resolution of diarrhea. Budesonide was stopped after 1 year of treatment. Eighteen months after the diagnosis, he is currently being followed in outpatient clinic, asymptomatic, but complaining of occasional constipation.