Renal · Year 2 · from Renal
Case 3: Ureteropelvic Junction Obstruction
Patient Presentation
A 24-year-old male presents to the emergency department with sudden onset of severe left flank pain that began 2 hours ago after drinking a large amount of water during a marathon.
History of Present Illness
- Severe, colicky left flank pain
- Nausea and one episode of vomiting
- No hematuria noted
- Similar but milder episodes in the past that resolved spontaneously
Physical Examination
- Blood pressure: 142/88 mmHg
- Heart rate: 96 bpm
- Left costovertebral angle tenderness
- Abdomen soft but tender in left upper quadrant
- No palpable masses
Workup
Laboratory Studies:
- Serum creatinine: 1.0 mg/dL (normal)
- Urinalysis: 1+ blood, no WBCs, no bacteria
- CBC: WBC 9,500/mcL (normal)
Imaging:
- CT abdomen/pelvis without contrast: Severe left hydronephrosis with dilated renal pelvis; no ureteral stones identified; ureter appears normal caliber below the ureteropelvic junction
Diagnosis
Ureteropelvic Junction (UPJ) Obstruction
Discussion
This case demonstrates the clinical relevance of urinary tract anatomy:
- Three Physiological Narrowings: The lecture describes three sites where kidney stones commonly lodge: the ureteropelvic junction (UPJ), the pelvic brim, and the ureterovesical junction (UVJ). Congenital UPJ obstruction occurs at the first narrowing.
- Renal Pelvis: The funnel-shaped renal pelvis collects urine from the major calyces and continues as the ureter
- Transitional Epithelium: The urothelium lining the renal pelvis can stretch but obstruction causes back-pressure transmitted to the nephrons
Treatment
- Pain management with ketorolac and opioids
- Urology consultation for definitive management
- Pyeloplasty (surgical repair of UPJ obstruction)
- Follow-up imaging to assess resolution of hydronephrosis
Clinical Pearl
UPJ obstruction often presents intermittently, particularly during periods of high urine output (after large fluid intake) when the fixed narrowing cannot accommodate increased flow. This "Dietl's crisis" is characteristic of the condition.
Image Reference
For visual reference of kidney anatomy and histology relevant to these cases, see:
- Wikimedia Commons: Category:Histology of kidney - Public domain images of nephron structure
- Radiopaedia: Hydronephrosis - Ultrasound images of dilated collecting system
- Wikimedia Commons: Category:Nephron - Diagrams of nephron components
Learning Points
- Cortical vs. Juxtamedullary Nephrons: The two nephron populations have different loop lengths, explaining why diseases affecting concentrating ability may spare some nephrons.
- End Arteries: The segmental arteries are end arteries without collateral circulation, making renal infarction possible with vascular occlusion.
- Urinary Tract Narrowings: The three anatomical narrowings (UPJ, pelvic brim, UVJ) are critical for understanding stone impaction and congenital obstructions.
- Two Capillary Beds: The unique arrangement of glomerular and peritubular capillaries allows independent regulation of filtration and reabsorption.