Non-Anion Gap Metabolic Acidosis - Case Study - The High-Output Ileostomy

Her anion gap is 9, her albumin is normal, and she is profoundly acidotic. A normal gap is not reassurance - it is a fork in the road, and the urine picks the branch. A case-based walk through one patient's non-gap acidosis, reasoning the way you would on rounds: confirm the gap, understand how the kidney makes bicarbonate, then use one urine calculation to decide whether the kidney is failing or compensating. A 44-year-old woman with Crohn disease and a six-week-old end ileostomy putting out two to three liters a day. What you'll learn: • How to confirm a normal anion gap and why the albumin has to be checked before you trust it • Electroneutrality on a Gamblegram - plasma must stay electrically neutral, so chloride rises exactly as bicarbonate falls • Renal ammoniagenesis step by step - glutamine to two ammonium and two bicarbonate, secretion into the tubular lumen, trapping in the collecting duct, and the bicarbonate returned to blood • The full etiology list, sorted into gastrointestinal, renal, ingestions and transients • The urine anion gap computed on her real numbers - sum the cations, subtract the chloride, and read the sign • Why a negative result is the normal, healthy answer, and what it proves about where the problem is • The positive result and what it points to - distal and type IV renal tubular acidosis, and early renal failure • When the urine anion gap cannot be trusted, and the urine osmolal gap that replaces it • Why urine pH alone is a poor substitute for either • Toluene as the trickiest ingestion on the list, because hippurate excreted with sodium and potassium makes the urine anion gap falsely positive • The plan - balanced crystalloids rather than normal saline, potassium and magnesium repletion, and slowing the output Key takeaway: Negative is normal - if the kidney is making ammonium, the problem is somewhere else. ⏱ Chapters: 0:00 A normal gap that is not reassuring 0:47 Act one - admission, a 44-year-old woman 3:06 The diagnostic pathway - an anion gap of nine 5:16 Act two - pathophysiology and electroneutrality 7:05 Ammoniagenesis, step by step 8:58 Act three - the etiologies, sorted 10:10 Computing the urine anion gap 10:55 What a negative result proves 12:34 Assessment and plan 13:47 When the urine anion gap is unreliable 14:59 The urine osmolal gap fallback 16:00 Urine pH pitfalls 17:11 Toluene - the trickiest ingestion 18:08 High-yield pearls Part of Teaching Service — Hospital Rounds: education for residents and advanced practice providers. For clinician and trainee education only. Not medical advice; verify against current guidelines and institutional protocols before applying to patient care. #UrineAnionGap #NonAnionGapAcidosis #CaseStudy #Ileostomy #HyperchloremicAcidosis #Ammoniagenesis #RenalTubularAcidosis #CrohnDisease #ClinicalReasoning #MedicalEducation