A 13-day-old infant developed bilateral hydroureteronephrosis, severe hyponatraemia, hyperkalaemia, and acidosis, as a result of urethral damage following circumcision. The hydroureteronephrosis and biochemical abnormalities normalized after resolution of the penile injury. Conclusion. Infants with urinary retention following circumcision may develop hydro-ureteronephrosis and electrolyte disturbances. An awareness of the potential dangers of circumcision may help to limit its complications.