Is it appropriate to administer diclofenac (Non-Steroidal Anti-Inflammatory Drug (NSAID)) injection to a patient with pain and difficulty in passing urine, potentially indicating urinary retention, without knowing the underlying cause of these symptoms?

Can Diclofenac Injection Be Given for Pain and Difficulty Passing Urine?

Yes, diclofenac injection can be given for pain associated with urinary tract conditions like renal colic, but you must first exclude urinary retention caused by bladder outlet obstruction or other non-obstructive causes, as NSAIDs including diclofenac can precipitate or worsen urinary retention in susceptible patients. 1

Clinical Decision Algorithm

Step 1: Identify the Underlying Cause of Urinary Difficulty

If the patient has acute renal colic (sudden severe flank pain radiating to groin/genitals):

• Diclofenac 75 mg intramuscular is the first-line treatment and should provide rapid pain relief within 30 minutes 2, 3
• This is a Grade A recommendation with high-quality evidence 2
• The British Medical Journal consensus strongly supports this approach for suspected kidney stones 4

If the patient has urinary retention (inability to void despite full bladder):

• Do NOT give diclofenac - NSAIDs are listed among drugs that can cause or worsen urinary retention 1
• NSAIDs impair bladder function through multiple mechanisms and are particularly risky in elderly men with prostatic enlargement 1
• Immediate catheterization and identification of the underlying cause (prostatic obstruction, neurogenic bladder, medication effects) is required 1

Step 2: Perform Rapid Clinical Assessment (Within 30 Minutes)

Essential examination findings to differentiate: 2

• Renal colic pattern: Unilateral flank pain, costovertebral angle tenderness, patient unable to find comfortable position, often with hematuria
• Retention pattern: Suprapubic fullness/tenderness, palpable bladder, inability to void despite urge, no flank pain

Red flags requiring immediate hospital admission: 2

• Fever or signs of systemic infection (suggests pyelonephritis or urosepsis)
• Hypotension or shock
• Anuria (complete inability to produce urine)
• Age >60 years with atypical presentation (consider ruptured abdominal aortic aneurysm)

Step 3: Administration Protocol for Confirmed Renal Colic

Dosing: 5, 3

• Give diclofenac 75 mg intramuscular as a single dose
• Intramuscular route is preferred over intravenous due to lower risk of dosing errors and technical complications 5
• Maximum daily dose is 150 mg (two 75 mg doses separated by at least 12 hours) 5

Follow-up monitoring: 2, 4

• Contact patient by phone 1 hour after injection to assess pain relief
• If pain persists after 60 minutes, arrange immediate hospital admission
• Instruct patient to increase fluid intake and strain urine to catch any stones

Step 4: Contraindications and High-Risk Situations

Absolute contraindications to diclofenac: 5

• Active peptic ulcer disease or history of GI bleeding
• Severe heart failure or recent myocardial infarction
• Severe liver failure (transaminases >3× upper limit of normal)
• Severe renal impairment (creatinine clearance <10 mL/min)
• Known allergy to NSAIDs or aspirin

Use alternative opioid analgesia (morphine + antiemetic) if: 4, 3

• Any of the above contraindications exist
• Pregnancy
• Significant cardiovascular disease
• Pre-existing renal impairment

Critical Caveats and Pitfalls

Renal function concerns: 6, 7

• Even a single dose of diclofenac can worsen subclinical acute kidney injury and potentially cause progression to chronic kidney disease 7
• In patients with suspected renal colic who may have obstructive uropathy, use the lowest effective dose for the shortest duration 6
• Diclofenac may be acceptable in mild-to-moderate CKD when used briefly, but avoid in severe renal impairment 6

Urinary retention risk: 1

• NSAIDs are documented to cause urinary retention, particularly in elderly men with benign prostatic hyperplasia 1
• Up to 10% of acute urinary retention episodes may be medication-related 1
• If urinary difficulty is due to retention rather than obstruction from a stone, diclofenac could worsen the condition 1

Stone-related paradox: 8

• While diclofenac effectively treats renal colic pain, it significantly reduces urinary excretion of glycosaminoglycans (GAGs), which are natural inhibitors of calcium oxalate crystallization 8
• This means diclofenac should not be used for long-term prevention of recurrent kidney stones 8

Monitoring for treatment failure: 2

• If adequate analgesia is not achieved within 60 minutes, this indicates either incorrect diagnosis or need for hospital-based intervention
• Consider alternative diagnoses: pyelonephritis, complicated UTI, non-urological causes of flank pain

When to Choose Opioids Instead

Prefer morphine sulfate with cyclizine (antiemetic) when: 4, 3

• NSAIDs are contraindicated
• Patient has significant renal impairment (use fentanyl specifically, as it doesn't accumulate active metabolites) 3
• Cardiovascular disease is present
• History of GI bleeding or peptic ulcer disease exists