When a kidney stone is an emergency

Why an obstructed stone with infection is dangerous

When a stone blocks the ureter, urine dams back up into the kidney. If that trapped urine becomes infected, the kidney acts like an abscess under pressure - bacteria and toxins are pushed directly into the bloodstream and the patient can rapidly develop sepsis. This condition is called obstructive pyelonephritis or pyonephrosis, and it is a true urological emergency. Mortality is meaningful if treatment is delayed.¹

International guidelines are clear: an obstructed, infected kidney must be drained urgently - usually within hours - by placing either a ureteric stent from below (cystoscopy) or a percutaneous nephrostomy tube from above through the flank, alongside intravenous fluids and broad-spectrum antibiotics. The stone itself is treated only later, once the infection has resolved.¹

Red-flag signs at a glance

Special situations that need earlier attention

• Pregnancy: any suspected stone in pregnancy warrants assessment at a hospital obstetric-emergency unit, because imaging options are limited and infection is more serious for mother and baby.
• Solitary or transplant kidney: a blockage in the only functioning kidney means no urine is being made. Any new stone pain needs same-day hospital review.
• Diabetes or immune suppression: infection can escalate more rapidly and fever may be less obvious.
• Anticoagulation: visible bleeding in a patient on warfarin, DOACs, or dual antiplatelet therapy should be assessed urgently.

What happens at the hospital

1. Triage & resuscitation

   Vital signs, intravenous fluids, pain relief, and blood tests (including kidney function and inflammatory markers). A urine sample is sent for culture.

2. Imaging

   A CT KUB confirms the stone location and size, identifies hydronephrosis, and rules out other causes of pain.

3. Urgent drainage if infected/obstructed

   If there is any suggestion of infection in an obstructed kidney, the kidney is drained urgently - usually with a ureteric stent under anaesthesia, or a percutaneous nephrostomy if a stent cannot be passed.¹

4. Antibiotics and observation

   Intravenous antibiotics are continued for 24-48 hours, tailored to the urine culture result, and the patient is monitored until stable.

5. Definitive stone treatment

   The stone itself is usually treated two to four weeks later, once the infection has fully cleared, with ureteroscopy, ESWL or PCNL depending on size and location.

When it is not an emergency

Many stones cause severe pain without any of these red flags. If pain is controlled by simple oral analgesia, you are not febrile, you are passing urine, and you are not vomiting, then outpatient review is appropriate - your GP can refer you to Dr Kooner's rooms for assessment within days.

A small, asymptomatic kidney stone found incidentally on a scan is not an emergency - it is a planned outpatient decision.

Related pages

Reference

1. Skolarikos A, et al. EAU Guidelines on Urolithiasis. European Association of Urology; 2025 edition. uroweb.org