Renal, Urology and Electrolytesniche
A 78-year-old man presents with three days of inability to pass urine and a painful lower abdomen, on a background of months of a poor stream and nocturia. A urethral catheter drains 1.8 L immediately. Blood tests taken before catheterisation show creatinine 410 µmol/L (60–110), urea 31 mmol/L, potassium 5.4 mmol/L, and an ultrasound shows bilateral hydronephrosis. Over the next four hours he passes 1.6 L of dilute urine.
Which one of the following is the most important complication to anticipate over the next 24 hours?