Discussion Author: Poorni M Manohar
Renal Forniceal rupture results from increased hydrostatic pressure in the renal pelvis due to outlet obstruction. The increased renal pelvis pressure ultimately results in the leakage of one or more renal fornices. Laplaceâ€™s law states T = ( P * R ) / M where T is the tension in the walls, P is the pressure difference across the wall, R is the radius of the cylinder, and M is the thickness of the wall. This helps to elucidate the physiological changes leading to renal forniceal rupture. The tensile stress imparted upon the dilated collecting system from back pressure increases with the size of the collecting system, thereby causing forniceal rupture in a more dilated system. As pressures exceeds the tensile strength of the forniceal tissues, eventually there is tissue disruption and extravasationn of urine.
The defect may be secondary to multiple etiologies, but is most commonly associated with ureteral calculi. Forniceal rupture was caused by ureteric stones in 80 cases (74.1%), malignant extrinsic ureteric compression in nine cases (8.3%), benign extrinsic ureteric compression in two cases (1.9%), pelvic-ureteric junction obstruction in two cases (1.9%), vesico-ureteric junction (VUJ) obstruction in one case (0.9%), bladder outlet obstruction in one case (0.9%) and iatrogenic causes in four cases (3.7%).(1) For patients in whom a ureteric stone was the cause of forniceal rupture, the level of obstruction was the proximal ureter in 24.3% of cases, distal ureter in 17.6% of cases, and Vesico-ureteral junction in 58.1% of cases. The mean stone size associated with renal forniceal rupture was found to be was 4.09 (2.0) mm.(1)
Clinically, the patient presents with nonspecific findings making it difficult to definitively suggest the diagnosis of renal forniceal rupture. Initial presentation includes the following symptoms: acute or persistent flank pain, hematuria, nausea, vomiting, fever, signs of peritoneal irritation, and/or sepsis.(2) Rupture of the renal pelvis must be considered when flank pain is unresponsive to treatment or if pain recurrs despite adequate analgesics. This diagnosis should also considered when persistent signs of obstruction are present in the absence of a stone detected on radiographic imaging.
IV contrast imaging is reuired to confirming the diagnosis. CT of the pelvis has a high radiation cost, but clearly demonstrates the defect in the renal calyx. Typical findings include irregularity of a single renal calyx; loss of the ability to discern renal sinus fat; asymmetrically-distributed perinephric stranding; and a discreet perinephric fluid collection.(1) These findings in combination with an appropriate history supports the diagnosis of renal forniceal rupture.
Perinephric stranding has been described as a sign of obstruction complicated by urinary tract infection, but the specificity of this finding is poor. In a study done with 97 patients, in whom urinalysis or culture was available at the time the CT was performed, only five (5.2%) showed the presence of urinary tract infection. Although, urinary tract infection should remain on a differential with radiographic findings of perinephric stranding, clinical findings of refractory pain, additional radiographic findings aforementioned, and laboratory evalution demonstrating sterile urine can assist a physician in the diagnosis of renal forniceal rupture.
The management of obstructive stones with forniceal rupture is conservative and recovery is most often uneventful. In general, most urinary calculi 4 mm or smaller pass with conservative treatment. Extracorporal shock wave lithotripsy is the method of choice for treating larger stones. One study compared the efficacy of stenting alone versus Urteroscopic Lithotripsy combined with stenting. Though both are effective, there were some differences in their utility. Stenting of the lithiasis-obstructed ureter is preferred in the acute phase of an infected or septic FR. Primary ureteroscopic lithotripsy and stone extraction, combined with ureter stenting, is a reliable, efficient, and safe method to treat definitely obstructive stones associated with forniceal rupture of a sterile system. (3)
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