Roger K. Low

Intestinal Oxalobacter formigenes colonization in calcium oxalate stone formers and its relation to urinary oxalate.

BACKGROUND AND PURPOSE Oxalobacter formigenes is an anaerobic commensal colonic bacterium capable of degrading oxalate through the enzyme oxalyl-CoA decarboxylase. It has been theorized that individuals who lack this bacterium have higher intestinal oxalate absorption, leading to a higher urinary oxalate concentration and an increased risk of calcium oxalate urolithiasis. We performed a prospective, controlled study to evaluate O. formigenes colonization in calcium oxalate stone formers and to correlate colonization with urinary oxalate and other standard urinary stone risk factors. PATIENTS AND METHODS Thirty-five first-time calcium oxalate stone formers were compared with 10 control subjects having no history of urolithiasis and a normal renal ultrasound scan. All subjects underwent standard metabolic testing by submitting serum and 24-hour urine specimens. In addition, all subjects submitted stool samples for culture and detection of O. formigenes by Xentr(ix) O. formigenes Monitor. RESULTS Intestinal Oxalobacter was detected in only 26% of the stone formers compared with 60% of the controls (p < 0.05). Overall, the average urinary oxalate excretion by the two groups was similar (38.6 mg/day v 40.8 mg/day). Among stone formers, however, there were statistically higher urinary oxalate concentrations in O. formigenes-negative patients compared with those testing positive (41.7 mg/day v 29.4 mg/day) (p = 0.03). Furthermore, all 10 stone formers with hyperoxaluria (>44 mg/day) tested negative for O. formigenes (p < 0.05). CONCLUSIONS Calcium oxalate stone formers have a low rate of colonization with O. formigenes. Among stone formers, absence of intestinal Oxalobacter correlates with higher urinary oxalate concentration and an increased risk of hyperoxaluria. Introduction of the Oxalobacter bacterium or an analog of its enzyme oxalyl-CoA decarboxylase into the intestinal tract may be a treatment for calcium oxalate stone disease.

Renal Intrapelvic Pressure During Percutaneous Nephrolithotomy and Its Correlation With the Development of Postoperative Fever

PURPOSE Systemic absorption of irrigation fluid containing bacteria or endotoxin may lead to fever and urosepsis after percutaneous nephrolithotomy. Although to our knowledge the exact method of absorption is undefined, intrapelvic pressure greater than 30 mm. Hg has been shown to result in pyelovenous-lymphatic backflow. We measured intrapelvic pressure during percutaneous nephrolithotomy and correlated pressure with postoperative fever and operative technique. MATERIALS AND METHODS Intrarenal pressure was measured with a transurethral 7Fr ureteral occlusion balloon catheter and a urodynamic system during percutaneous renal access, rigid and flexible nephroscopy, and intracorporeal lithotripsy. Postoperative fever was correlated with elevated intrarenal pressure, stone type and surgical technique. RESULTS Enrolled in this study were 18 women and 13 men. Pressure greater than 30 mm. Hg was recorded in 8 patients (26%). Elevated pressure occurred under 2 conditions, namely incomplete positioning of the nephroscopy sheath within the collecting system and endoscopy through a narrow infundibulum. In 13 cases (42%) a fever of 38C or greater developed postoperatively. Elevated pressure did not correlate with fever. However, of those undergoing percutaneous nephrolithotomy for the removal of infection versus noninfection stones 64% and 24%, respectively, had fever postoperatively. CONCLUSIONS Renal intrapelvic pressure generally remains low during percutaneous nephrolithotomy. Elevated pressure was associated with incomplete nephroscopy sheath positioning within the collecting system and endoscopy through an infundibular narrowing. There was no association of renal pressure greater than 30 mm. Hg with fever but postoperative fever and percutaneous nephrolithotomy done for infection related stones correlated significantly.

Case Reports: Nephrostomy Tract Tumor Seeding Following Percutaneous Manipulation of a Ureteral Carcinoma

We report a case of nephrostomy tract tumor seeding following percutaneous nephrostomy tube placement and endoscopic manipulation of ureteral carcinoma. While never previously reported to our knowledge, tumor seeding is a potential risk of percutaneous endoscopic management of upper tract urothelial carcinomas.

URIC ACID–RELATED NEPHROLITHIASIS

Abnormalities in uric acid metabolism are associated with uric acid and calcium oxalate urolithiasis. Clinical stone formation depends on multiple identifiable risk factors that affect uric acid and calcium oxalate solubility. The understanding of urinary pH is critical to direct appropriate treatment of uric acid-related nephrolithiasis. Understanding uric acid metabolism and the pathophysiology of uric acid and calcium oxalate stone formation leads to a rational treatment approach to uric acid and hyperuricosuric calcium oxalate stone disease.

IMMUNOHISTOCHEMICAL ANALYSIS OF BCL-2 PROTEIN EXPRESSION IN RENAL CELL CARCINOMA

PURPOSE To investigate the incidence, extent, and distribution of bcl-2 protein expression in human renal cell carcinomas. MATERIALS AND METHODS Using immunohistochemical tissue staining techniques, bcl-2 protein expression was analyzed in archival nephrectomy specimens removed for renal cell carcinoma or trauma and in 3 renal cell carcinoma cell lines. RESULTS Normal kidneys demonstrated bcl-2 immunopositivity primarily within the cytoplasm of distal tubule cells. Only rare and minor staining of the proximal tubular cells, thought to be the origin of renal cell carcinoma, was noted in histologically normal controls and areas adjacent to tumor. In contrast, bcl-2 protein expression was demonstrated in 70% of renal cell carcinomas and in all 3 experimental cell lines. CONCLUSIONS Bcl-2 is a proto-oncogene known to regulate apoptosis (programmed cell death). Bcl-2 protein is overexpressed in the majority of renal cell carcinomas examined. Bcl-2 overexpression may have a role in tumorigenesis and may explain the relative resistance of renal cell carcinoma to chemotherapeutic agents and to radiation therapy.

Extraperitoneal Laparoscopy-Assisted Percutaneous Nephrolithotomy in a Left Pelvic Kidney

Treatment of urolithiasis within a pelvic kidney presents a technical challenge. We report an extraperitoneal laparoscopy-assisted percutaneous approach to access the lower-pole calix of a pelvic kidney for percutaneous nephrolithotomy.

Ureteroscopic treatment of renal calculi

Although ureteroscopic treatment of renal calculi is safe and effective. it is relatively inefficient compared with ESWL and PCNL. It should be considered primary therapy for patients with lower pole stones who have adverse ESWL characteristics and patients who are not suitable candidates for PCNL. There are also numerous clinical situations, as outlined previously, where the ureteroscopic approach is favored over other treatment modalities.

Urolithiasis risk factors in the bariatric population undergoing gastric bypass surgery

BACKGROUND Previous studies have suggested an increased risk of forming symptomatic urolithiasis after Roux-en-Y gastric bypass (RYGB) attributed to the development of hyperoxaluria. The objective of our investigation was to evaluate changes in the urine milieu after RYGB that might explain the increased risk of urolithiasis. METHODS Patients underwent serum and urine chemistry tests 1 week before and 6 months after RYGB at a university hospital. The postoperative urolithiasis risk factors were compared with the preoperative values. Statistical analysis was performed using paired t tests. Significant changes were identified as P ≤ .05. RESULTS A total of 38 patients (7 men and 31 women) submitted samples both before and after RYGB. The mean patient weight had decreased from 131 kg to 92 kg. The mean serum creatinine decreased from .83 to .72 mg/dL (P = .0004). Urinary changes known to increase the risk of urolithiasis include a decrease in volume (2-1.5 L/d, P = .03), an increase in calcium (139-182 mg/d, P = .04), and an increase in oxalate (38-48 mg/d, P < .001). The urinary supersaturation indexes for calcium oxalate (4.9-10.5, P < .001) increased. CONCLUSION Our results confirm that patients undergoing RYGB develop changes in the urinary milieu predisposing them to forming urinary stones. Urolithiasis risk is multifactorial and is related to more than just hyperoxaluria. A patients long-term risk of developing stones and the effect on renal function is unknown. Preoperative counseling of patients regarding their risk of forming stones and dietary counseling to minimize their risk of developing stones postoperatively is warranted.

Correlation of ureteral stone measurements by CT and plain film radiography: Utility of the KUB

BACKGROUND AND PURPOSE The practice of utilizing helical CT to evaluate patients suspected of renal colic is increasing. Little is known about the accuracy of CT in estimating stone size or the utility of an accompanying plain abdominal radiograph (KUB film). The purpose of our study was to compare ureteral stone size estimation by helical CT and plain film and determine whether a KUB film provides additional information useful in patient management. PATIENTS AND METHODS Thirty consecutive patients (17 male, 13 female) having both a helical CT and a KUB study for evaluation of renal colic secondary to ureteral calculi comprised the study population. Calculus number, location, and dimensions were determined from these images. Stone dimensions were measured using electronic calipers on a picture archiving and communications system. Information found by KUB and CT was compared, and both sets of stone measurements were correlated with patient outcome. RESULTS The mean maximal stone transverse diameter and length were similar on CT and plain film: 5.8 mm v 5.8 mm and 9.5 mm v 8.9 mm, respectively (P = 0.57 and 0.29, respectively). The mean anteroposterior stone diameter on CT of 6.8 mm was statistically greater than the transverse diameter as measured by both CT and KUB, which were 5.8 mm and 5.8 mm (P = 0.0002 and 0.0007, respectively). Eleven patients spontaneously passed their stones, while 19 patients required intervention. Patient outcome, as predicted by transverse stone width, was similar for CT and KUB data. CONCLUSIONS The management of patients with ureteral calculi relies on estimated stone size and the stones potential for spontaneous passage. Stone dimensions estimated by CT are similar to the size determined by plain film radiography. Although plain film radiography does not provide information on stone dimensions beyond that obtained with CT, it does reveal precise stone location and radiolucency, data helpful in following and treating patients.

Laparoscopic use of the ureteral illuminator

Laparoscopic identification of the ureters is complicated by decreased tactile sensation and magnified video imaging. We report our experience in placing a ureteral illuminator to aid in ureteral identification prior to six laparoscopic urologic procedures. The ureteral illuminator facilitated laparoscopic ureteral identification during five nephoureterectomies and one ureterolithotomy. Illuminator placement required a minimum of anesthetic time and resulted in no complications. Preoperative placement of a ureteral illuminator aids laparoscopic ureteral identification and may reduce the incidence of inadvertent ureteral injury.