An elderly female patient presents to the emergency department with acute onset left flank pain radiating to the groin. What is the most appropriate imaging protocol for initial evaluation?

Appeared in: INI-CET EXAM -2026

Explanation

Non-contrast CT (NCCT) is the gold standard and 'method of choice' for diagnosing suspected kidney stones due to its superior accuracy.
NCCT offers high speed, sensitivity (greater than 95%), and specificity, allowing for the detection of stones regardless of their type, size, or location.
In an elderly patient, NCCT is particularly valuable as it can rapidly identify or exclude other life-threatening causes of flank pain, such as an abdominal aortic aneurysm.
The standard protocol begins with an NCCT to visualize the stone. A contrast-enhanced CT (CECT) may follow if further evaluation of kidney function, obstruction, or other abnormalities is required.

Option A: MRI is not the primary tool for detecting kidney stones because it does not visualize calcifications well. It is also more time-consuming and expensive than a CT scan.
Option B: While ultrasound is a good, radiation-free initial test, it is less sensitive than NCCT, especially for detecting small stones or those located in the middle of the ureter. Given the need for a definitive diagnosis in an elderly patient, NCCT is superior.
Option C: This is an outdated protocol. A plain X-ray (KUB) cannot detect radiolucent stones (e.g., uric acid stones) and its view is often limited by overlying bowel gas and bones, making it an unreliable initial test.

Clinical Relevance

Nursing practice connection: Prioritize focused assessment, early escalation, and real-time monitoring when managing Initial diagnostic imaging for suspected urolithiasis (kidney stones) in acute care settings.
Nurses in the emergency department play a key role in preparing patients for urgent CT scans, which includes assessing for contrast allergies and checking renal function (creatinine levels) before a potential CECT.
Prompt and accurate diagnosis of urolithiasis is critical for initiating appropriate pain management (e.g., NSAIDs, opioids) and determining the need for urological intervention.
What if? If the patient were a 28-year-old female in her second trimester of pregnancy, the most appropriate initial imaging would be a renal ultrasound to avoid exposing the fetus to ionizing radiation. NCCT would be reserved for rare, complex cases where the benefit outweighs the risk.

How to Approach the Question

Analyze the patient's presentation: 'Acute onset left flank pain radiating to the groin' is the classic description of renal colic from a kidney stone.
Identify the core question: It asks for the 'most appropriate' initial imaging test, which implies the test with the highest diagnostic accuracy for this condition.
Evaluate the options based on their known utility for detecting kidney stones.
Compare the modalities: MRI is poor for stones, X-ray is insensitive, and Ultrasound is good but less sensitive than CT.
Recall that Non-Contrast CT (NCCT) is the gold standard for speed and accuracy in diagnosing urolithiasis in non-pregnant adults.
Select the option that includes the gold standard test as the initial step.

Concept Tested & Keywords

Concept Tested: Initial diagnostic imaging for suspected urolithiasis (kidney stones).
Stem keywords: elderly female, acute onset, left flank pain, radiating to the groin, imaging protocol
Lead-in keywords: most appropriate
Clinical cues: The patient's presentation of acute flank pain radiating to the groin is a classic sign of renal colic, pointing towards a diagnosis of kidney stones (urolithiasis).

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E6 Medicine Davidson Principles Practice 24e p. 409-411

E6 Gynecology Williams p. 47-72

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