#4238 UNEXPLAINED METABOLIC ACIDOSIS - A DIAGNOSTIC DILEMMA
Authors: Kumar Abhishek 
Published: June 2023

Abstract

Background and Aims
Metabolic Acidosis is a common condition for which nephrology consult is sought. Most often the etiology is quite obvious like renal failure, diabetic ketoacidosis, lactic acidosis etc. We describe a case of high anion gap metabolic acidosis, unresponsive to medical management requiring hemodialysis, where finding the etiology became a diagnostic challenge because of medical and social reasons prevailing in this eastern part of India.

Method
A 55 year old obese gentleman came to emergency department at 3 am with complains of restlessness, pain abdomen and chest discomfort for last 4-6 hours. On clinical examination he had tachycardia with normal blood pressure and oxygen saturation. His sensorium was normal and systemic examination did not reveal any major abnormality. A possibility of acute cardiac event was considered but his ECG showed sinus tachycardia, echocardiography did not show any wall motion abnormality and Troponin I was less than 0.01 ng/mL. His blood gases showed an uncompensated metabolic acidosis with an anion gap of 21 (pH 7.19 / pCO2 44 / HCO3 15). The laboratory parameters showed a serum creatinine of 0.9 mg/dL, random blood sugar of 130 mg/dL. Any history of poisoning or drug overdose was denied by patient's attendants. Pending further workup patient was admitted in intensive care unit and correction of metabolic acidosis was started with intravenous sodium bicarbonate.

Results
The metabolic acidosis initially improved with medical management but within next 6 hours patient again had severe metabolic acidosis. Meanwhile patient's sensorium worsened and he had an episode of seizure. Patient was intubated and mechanical ventilation started. Within 30 minutes patient had status epilepticus which ultimately required intravenous thiopentone. Hemodialysis was started for correction of metabolic acidosis. Patient's history was re-evaluated. On persistent questioning his attendants admitted that patient had consumed alcohol 4-5 hours before the symptoms started. It is important to mention here that consumption of alcohol is a punishable offence in Bihar which a state in eastern part of India. Despite alcohol being completely banned in this part of country illicit alcohol is smuggled and consumed by some. Illicit alcohol is prone to be adulterated and sub-standard. It was because of this fact that patient's attendants suppressed the facts. Also alcohol consumption is a valid ground for rejection of medical insurance claims because of obvious reasons. After obtaining the complete history a possibility of consumption of alcohol adulterated with methyl alcohol was very likely. Serum methyl alcohol estimation was not available at our institute and patient had already received hemodialysis hence it was not done. With patient already having seizures MRI (Magnetic Resonance Imaging) of brain was done. MRI brain revealed altered hyperintense signal with cytotoxic edema in bilateral basal ganglia predominantly putamen. Subcortical white matter in bilateral cerebral hemisphere and bilateral optic nerve head showed restriction on diffusion weighted imaging. These typical features on MRI were highly suggestive of methanol toxicity. These MRI features along with the clinical scenario and history of illicit alcohol intake helped us reach the diagnosis of methanol toxicity. Patient was managed with hemodialysis sessions to remove methanol from blood until he improved clinically.

Conclusion
The etiology of the high anion gap metabolic acidosis turned out to be methanol toxicity. Typical MRI brain findings helped confirm the diagnosis. Our case highlights the importance of obtaining the correct medical history and how social and medicolegal issues sometimes become a hindrance to obtaining the same.