Confusable diagnoses · PANCE / PANRE

Urolithiasis vs Acute Pyelonephritis

Urolithiasis and Acute Pyelonephritis are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Urolithiasis vs Acute Pyelonephritis at a glance

  • Urolithiasis: Renal/ureteral calculi causing acute flank pain; calcium oxalate most common.
  • Acute Pyelonephritis: Upper urinary tract infection involving renal parenchyma; fever, flank pain, CVA tenderness.
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Side-by-side comparison

FeatureUrolithiasisAcute Pyelonephritis
At a glanceRenal/ureteral calculi causing acute flank pain; calcium oxalate most common.Upper urinary tract infection involving renal parenchyma; fever, flank pain, CVA tenderness.
Classic presentationWrithing patient with acute severe flank pain radiating to groin + hematuria = textbook ureteral stone.; Sudden severe colicky flank pain radiating to groin/testicle/labia; Patient writhing, unable to find comfortable position (contrast with peritonitis where patients lie still); Nausea and vomiting; Dysuria, urinary frequency/urgency…Fever + flank pain + CVA tenderness + pyuria = pyelonephritis. Add hypotension or organ dysfunction = urosepsis.; Fever (often >38.5°C), chills, rigors; Flank or back pain (unilateral or bilateral); Nausea and vomiting; Lower UTI symptoms — dysuria, frequency, urgency — preceding or accompanying upper tract symptoms; Malaise, fatigue,…
Workup / key labsCT-confirmed urinary tract calculus with consistent clinical presentation. Size and location predict spontaneous passage: <5 mm pass ~80%, 5-10 mm ~50%, >10 mm rarely; distal ureteral stones pass more often than proximal.; Urinalysis with microscopy — hematuria (gross or microscopic), pH (acidic favors uric acid; alkaline favors…Clinical diagnosis: classic symptoms (fever, flank pain, CVA tenderness) + pyuria + bacteriuria. Urine culture confirms organism and susceptibility.; Urinalysis with microscopy — pyuria, bacteriuria, WBC casts (specific for upper tract), nitrites, leukocyte esterase; Urine culture and susceptibility — ALWAYS obtain (vs cystitis where…
ImagingNon-contrast CT abdomen/pelvis (low-dose) — gold standard; identifies stones >1 mm, hydronephrosis, alternative diagnoses; Renal ultrasound — first-line in pregnancy and children; reasonable initial test in adults to detect hydronephrosis (lower sensitivity for small ureteral stones); KUB plain film — limited; misses radiolucent uric…Imaging not required in most uncomplicated pyelonephritis with prompt improvement; CT abdomen/pelvis with contrast if: failure to improve after 48-72 h of appropriate antibiotics, sepsis, suspected obstruction or abscess, recurrent pyelonephritis, atypical course, history of stones, men; Renal ultrasound — first-line in pregnancy and…
First-line treatmentPain control — NSAIDs (ketorolac IV/IM, ibuprofen) are first-line; superior to opioids and reduce ureteral spasm; AVOID in CKD, dehydration, or single kidney; Opioids (morphine, hydromorphone) as second-line or adjunctive analgesia; Antiemetics (ondansetron, metoclopramide); IV fluids only if dehydrated — aggressive forced diuresis does…Outpatient (mild, hemodynamically stable, tolerating oral, no obstruction):; Fluoroquinolone (pyelo) — ciprofloxacin 500 mg PO BID × 7 days or levofloxacin 750 mg PO daily × 5 days — first-line if local resistance <10%; TMP-SMX DS PO BID × 14 days if susceptible (avoid empiric if resistance unknown); Consider initial single dose of…

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Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.