A 68-year-old man sits forward on the stretcher, shifting every few seconds as waves of pain cross his right flank. He says he has barely passed urine since yesterday, and his daughter noticed he has been unusually foggy this morning. The monitor shows a regular rhythm, but his creatinine is more than twice its recorded baseline. The bedside scan is ready, and the next move has not yet been made.

— What’s your move? Read on.

Before you read
  • What finding makes a urinary obstruction an infected emergency?
  • When does a catheter solve the problem—and when does it miss the obstruction?

When to Think of It

Consider obstruction with acute urinary retention, flank pain or renal colic, oliguria/anuria, unexplained acute kidney injury, or recurrent UTI with hydronephrosis. Check for lower-tract retention with bladder scan; renal ultrasound or CT helps identify upper-tract obstruction and its cause.

Sick or Not Sick

The pivotal call is whether obstruction is infected or causing threatened renal function. Fever or sepsis with an obstructed collecting system, bilateral obstruction, obstruction of a solitary functioning kidney, anuria, or significant AKI calls for urgent urology involvement and decompression—not antibiotics or observation alone.

The First Fifteen Minutes

  • If hypotensive, confused, or poorly perfused: establish IV access, monitor, send CBC, metabolic panel, urinalysis/culture, and lactate as indicated; give balanced crystalloid in 500–1,000 mL IV boluses with reassessment if hypovolemic, particularly cautiously in heart or renal failure.
  • If severe pain: fentanyl 0.5–1 mcg/kg IV, titrated every 5–10 minutes to effect, because opioid analgesia can control renal colic while definitive evaluation proceeds.
  • If a distended bladder or acute retention is suspected: place a urethral catheter; if passage meets resistance or there is known urethral injury, stop and seek urologic guidance rather than force it.
  • If infected obstruction is suspected: obtain cultures without delaying treatment and give ceftriaxone 1–2 g IV, then arrange urgent drainage; it treats common urinary pathogens but does not relieve the obstruction.
  • If hyperkalemia causes ECG changes or is severe: give calcium gluconate 1 g IV (10 mL of 10% solution), repeat if ECG changes persist; give regular insulin 10 units IV with dextrose 25 g IV, because insulin shifts potassium intracellularly. Add nebulized albuterol 10–20 mg if appropriate; it provides an additional intracellular shift.
  • Do not let symptom improvement, antibiotics, or a Foley catheter falsely reassure you when the upper tract remains obstructed.

Definitive Care & Disposition

Infected obstruction requires urgent source control—usually ureteral stent or percutaneous nephrostomy—plus IV antibiotics and admission. Anuria, AKI, bilateral obstruction, a solitary kidney, uncontrolled pain/vomiting, or significant electrolyte disturbance generally warrants admission and urgent urology consultation. Stable patients with uncomplicated unilateral obstruction may be discharged only if pain is controlled, renal function is acceptable, there is no infection or high-risk anatomy, and follow-up is reliable. A Foley treats bladder-outlet obstruction, not an obstructed ureter.

How This One Kills

Treating an infected obstructed kidney with antibiotics alone. Bacteria remain trapped behind the blockage; deterioration to septic shock can occur despite apparently appropriate antimicrobial therapy.
The Differential — What Else Looks Like This
  • Pyelonephritis without obstruction — no obstructed collecting system; missing obstruction delays source control.
  • Renal colic without high-risk obstruction — unilateral stone with preserved renal function and no infection; overcalling risk can lead to unnecessary intervention.
  • Acute tubular injury — AKI without hydronephrosis or retention; attributing it to obstruction delays the actual renal work-up.
  • Abdominal aortic aneurysm — vascular risk, pulsatile mass, or unexplained shock; mislabeling it as renal colic can be fatal.

The Second-Day Story

Older adults may have delirium, falls, nausea, or vague abdominal discomfort rather than flank pain; neuropathy, immunosuppression, or analgesics can blunt pain and fever. A patient with obstruction of a solitary kidney—or bilateral obstruction—may present mainly with low urine output and rising creatinine. When the story is quiet but renal function or urine output is changing, check bladder volume and image the kidneys rather than relying on symptoms.
Back to Our Patient
Back to our 68-year-old man with right flank pain, low urine output, and new fogginess. Recognize possible obstruction with AKI; risk-stratify him as high risk until infection, bilateral disease, and solitary-kidney obstruction are excluded. Check a bladder scan and renal imaging, obtain urine and blood studies, and give fentanyl for severe pain while monitoring his renal function and electrolytes. If imaging shows an infected obstructed system, give IV antibiotics and arrange urgent urologic decompression; if the bladder is distended, catheterize, but confirm that this resolves the obstruction. He is admitted for AKI and urgent urology evaluation rather than discharged based on pain relief.
Patient Presentation to Attending
How you’d present this patient on the floor — tight, pertinent positives and negatives, no rambling
“This is a 68-year-old man presenting with acute right flank pain, oliguria, and confusion. His daughter reports markedly reduced urine output since yesterday and new fogginess this morning; he has no known trauma or dysuria. He is uncomfortable but currently hemodynamically stable, with right flank tenderness and no peritoneal signs. His creatinine is more than twice baseline, and we are checking potassium, urinalysis, bladder volume, and renal imaging now. I’m concerned about obstructive uropathy with AKI and will assess for infection and high-risk anatomy. I’ll treat his pain, catheterize if retention is demonstrated, and involve urology urgently if imaging confirms upper-tract obstruction or infection. He needs admission if AKI or a high-risk obstruction is confirmed.”

Study Directive

  • Draw a two-branch pathway from memory: bladder-outlet obstruction versus upper-tract obstruction, including the first test and definitive intervention for each.
  • Work through three cases: infected stone, retention with AKI, and obstruction of a solitary kidney; state the disposition and source-control plan for each.
  • Review your local hyperkalemia treatment protocol and recite the calcium, insulin/dextrose, and albuterol doses without looking.

Recent Literature