What is Renal Colic
Renal colic is an acute pain syndrome characterized by the abrupt onset of severe, unilateral flank pain that radiates into the groin or genitals, typically caused by obstruction of the upper urinary tract. 1
Clinical Definition and Pathophysiology
Renal colic represents a medical emergency that accounts for approximately 2% of emergency department admissions. 2 The condition is defined by:
- Sudden onset of severe unilateral flank pain radiating toward the abdomen, groin, or external genitals 1, 3
- Pain severity is often described as intense and can be accompanied by nausea or vomiting in approximately half of cases 3
- Associated symptoms include frequent urination, dysuria, oliguria, and hematuria 4
The underlying mechanism involves obstruction of the upper urinary tract, which causes increased hydrostatic pressure above the obstruction site. 3 This pressure increase triggers the severe pain characteristic of renal colic. Interestingly, prolonged stone impaction activates autoregulatory mechanisms that lower upper tract pressure, which can paradoxically limit pain over time. 3
Etiology
In adults, urinary stones (urolithiasis) cause renal colic in 80-85% of cases. 5, 2 The remaining 15-20% result from:
- Intrinsic obstructions (10%): pyeloureteral junction stenosis, ureteral tumors, or malformations 5, 2
- Extrinsic obstructions (5-10%): pelvic tumors, lymphadenopathy, retroperitoneal abnormalities, or intestinal abnormalities 5, 2
Diagnostic Features
The diagnosis centers on clinical presentation, though supporting evidence strengthens certainty:
- Hematuria is present in over 80% of patients with acute renal colic, supporting the diagnosis 1
- Pain location and radiation depend on the stone's position within the urinary tract 3
- Vital signs assessment is essential to exclude shock and systemic infection 1
Important Differential Diagnoses
Critical alternative diagnoses must be excluded, particularly in specific populations:
- Patients over 60 years: Consider leaking abdominal aortic aneurysm 1
- Women with delayed menses: Consider ectopic pregnancy 1
- Fever with renal colic: Consider obstructive pyelonephritis, which represents a true surgical emergency requiring urgent drainage 2
Clinical Significance
Renal colic is common in industrialized nations, affecting up to 15% of white men and 6% of women during their lifetime. 4 The recurrence risk is substantial, reaching 40% within 5 years and 50% within 10 years. 3, 4
Risk factors precipitating acute episodes include dehydration with reduced urine output, increased protein intake, heavy physical exercise, and certain medications. 4
Common Pitfalls
Atypical presentations can delay diagnosis, especially in elderly patients. 2 Clinicians must maintain high suspicion even when classic symptoms are absent, as delayed recognition of complicated renal colic (particularly obstructive pyelonephritis) can lead to serious morbidity. 2