Renal Colic in the ED - Diagnosis

Renal colic should be considered the most likely diagnosis in a patient with:

• Age under 50
• A typical history of renal colic
• No haemodynamic instability
• Non-tender abdomen
• Blood on urinalysis (but no nitrites or leucocytes).

Alternative diagnoses, especially aortic aneurysm, should always be considered in the older patient or those with atypical presentations.

Renal colic associated with fever, pyuria, or significant tenderness suggests infected obstructed kidney and is a urologic emergency requiring urgent referral for potential renal decompression.

NOTE: Absence of blood on U/A makes renal colic less likely but does not exclude it. Up to 15% of patients with renal colic do not have haematuria.

Pathology tests

• Urinalysis: to confirm haematuria and to check for nitrites and leucocytes
• UEC: to document renal function
• FBC: if any suggestion of infection (fever, tenderness, positive U/A)
• Mid Stream Urine (MSU): if evidence of infection

Urate, calcium, LFT’s are NOT routinely necessary. Serum urate does not correlate with presence of uric acid stones.

Imaging

All patients with new onset renal colic don't necessarily require definitive imaging. Radiation in younger patients should be avoided if possible. Patients with recurrent episodes generally do not require repeat imaging.

Indications for CT-KUB during ED presentation:

• Clinical evidence of associated UTI
• Age > 50 with no recent renal calculi
• Recurrent or unremitting pain
• Clinically not absolutely typical for renal colic
• Single kidney
• Renal impairment
• Renal transplant

Ultrasound (“ultrasound KUB”) may be the best first test either in ED or as OP. Particularly for follow up imaging or pregnancy. Ultrasound will demonstrate hydronephrosis, and can show intra-renal or very proximal ureteric calculi, but is generally poor at imaging the ureter. Bedside ultrasound may be useful in identifying hydronephrosis and excluding AAA. However, ultrasound is poorly sensitive for ureteric calculi.

Plain KUB is of minimal benefit in confirming or excluding the diagnosis and should not be ordered routinely. Exceptions may be in a patient with a known radio-opaque stone where x-ray may show stone progression 

Non-contrast CT urography (“CT-KUB”) is very sensitive for detecting calculi and demonstrates obstructed ureters and secondary signs of obstruction. It may also detect other pathology mimicking renal colic but carries the risk for any ionising radiation.

The West Australian Diagnostic Imaging Pathways are a great resource and the algorithm is here.