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Biomedical subjects

Manoj Monga

Publications and source records attributed to Manoj Monga.

At least 19 recordsLinked to original sources
PubMed2006

In vitro evaluation of ureteral stent compression.

OBJECTIVES: To evaluate the force required to radially compress ureteral stents and the impact of compression on stent performance across a broad range of stent sizes and manufacturers. METHODS: Fourteen ureteral stents ranging in size from 6F to 10.3F were evaluated for radial compression using an MTS Micro Bionix Testing System using Testworks II software, 5N load cell, vibration isolation table, and socket set screws with rounded caps. Radial compression was exerted in 0.2-mm increments. Cycles of compression and a 100-second hold time were repeated for each stent to maximal compression. Three trials were completed for each stent. The Young's Modulus, E, was calculated from each trial using the engineering stress. Simultaneous flow data using normal saline were collected for the Amplatz stent. RESULTS: The Cook C-Flex (E = 30,355 +/- 910 Pa), Microvasive Percuflex Plus 6F (E = 28,973 +/- 250 Pa), Cook EndoSof (E = 28,403 +/- 471 Pa), and Fossa Open Lumen (E = 28,627 +/- 5,338) were the most resistant to compression and the Cook Amplatz 10.2F (E = 11,922 +/- 220 Pa) and Microvasive Percuflex Plus 10.3F (E = 8,247 +/- 286 Pa) were the least resistant to compression. Stress relaxation occurred similarly in all stents. Flow through the Cook Amplatz stent decreased at a rate of 5 mL/s/mm of compression linearly (R2 = 0.95). CONCLUSIONS: Stents resistant to radial compression are critical for function in the face of extrinsic ureteral obstruction. The Cook C-Flex ureteral stent resisted extrinsic compressive forces best. Although large-lumen stents are often used in this clinical situation, they were the most susceptible to compressive forces.

Equipment Design↗
PubMed2006

Heterotopic ossification of percutaneous nephrostomy tract.

Heterotopic ossification is a rare, abnormal formation of true bone within extraskeletal soft tissues and is a common complication after musculoskeletal trauma or orthopedic procedures. We report a case of heterotopic ossification of a percutaneous nephrostomy tract causing flank pain and masquerading as a retained nephrostomy catheter in a young steroid-dependent man with sarcoidosis 2 years after percutaneous nephrolithotomy. The patient's underlying sarcoidosis combined with local tissue ischemia likely contributed to this rare complication.

Adult↗
PubMed2006

Irrigation and drainage properties of three-way urethral catheters.

OBJECTIVES: To evaluate in an in vitro study the irrigation and drainage capabilities of a variety of available catheters. Three-way Foley catheters are used when irrigation of the bladder is anticipated to prevent or manage blood clots in the bladder. METHODS: Six operators applied maximal one-handed pressure irrigation with a catheter-tip syringe through the irrigation and drainage ports of the Bardex and Dover three-way catheters (16F to 26F). Maximal manual irrigation flow was recorded using a flowmeter. Continuous gravity irrigation and drainage flows were measured by suspending a 2-L irrigation bag 80 cm above the catheters and fastening an artificial bladder to the drainage tip of each Foley catheter with the catheter balloon inflated to 30 mL. RESULTS: The Bardex 22F and 24F catheters had superior manual irrigation using the irrigation port (maximal urinary flow rate 8.9 +/- 1.3 mL/s and 9.5 +/- 1.5 mL/s, respectively, P < 0.000001) compared with the Dover 22F and 24F catheters. The Bardex and Dover 22F catheters (maximal urinary flow rate 29.0 +/- 1.9 mL/s and 29.3 +/- 1.9 mL/s, respectively, P = 0.66) and 24F catheters (maximal urinary flow rate 30.5 +/- 2.0 mL/s and 30.6 +/- 1.2 mL/s, respectively, P = 0.83) performed equally in manual irrigation using the drainage port. The Bardex 22F (average flow rate 1.6 +/- 0.1 mL/s, P < 0.00001) and 24F (average flow rate 1.7 +/- 0.0 mL/s, P < 0.000001) catheters exhibited better continuous irrigation and flow than the Dover 22F and 24F catheters. CONCLUSIONS: Three-way catheters are placed in situations in which efficient bladder irrigation is essential for patient safety. The Bardex 22F to 26F catheters optimized continuous bladder irrigation of the catheters tested.

Catheterization↗
PubMed2006

Merkel cell carcinoma metastatic to testis.

Merkel cell carcinoma is an uncommon, highly aggressive, neuroendocrine tumor that derives from cutaneous Merkel cells involved in proprioception. It is an extremely aggressive and rapidly fatal cancer. We report a rare case of Merkel cell carcinoma metastatic to the testis with prolonged survival.

Carcinoma, Merkel Cell↗
PubMed2006

Ureteral stents: coil strength and durometer.

OBJECTIVES: To evaluate the coil strength before and after urine exposure and the stiffness of commercially available double-J ureteral stents because both properties may affect stent performance and patient comfort. METHODS: Twelve commercially available 6F ureteral stents were tested for coil strength before and after 30 days of urine exposure. The proximal end of each stent was inserted through a 2-mm hole in bologna, allowed to recoil, and then pulled using a handheld force gauge. Ten different commercially available ureteral stent models were tested for tensile strength using an MTS MicroBionix Testing System and Testworks II software and a 5 N load cell. RESULTS: The Cook Black Silicone and Cook C-Flex stents had the strongest coil strengths before urine exposure at 0.480 +/- 0.0 lb (P < or = 0.0006) and were also the stents that had the greatest decrease in coil strength after urine exposure. After urine exposure, the weakest stent was the Applied Vertex stent at 0.088 +/- 0.008 lb (P < or = 0.02) and the strongest was the Cook Endo-Sof AQ at 0.223 +/- 0.014 lb (P < or = 0.03). Calculating the Young's modulus, E, the Cook C-Flex stent was the stiffest (E = 1472 +/- 196 KPa) and the Cook Black Silicone was the least stiff (E = 122 +/- 18 KPa). The stent models that demonstrated consistent E values across different lot numbers were the Circon Double J stent and Bard InLay. CONCLUSIONS: Ureteral stents can be differentiated according to their coil strength and stiffness. The impact of these properties on stent performance and patient comfort deserve additional evaluation. The significant variability found in stent stiffness among stents from different lot numbers suggests poor quality assurance in biomaterials or stent processing and increases the complexity of cross-stent comparisons.

Elasticity↗
PubMed2006

Genetic heritability of urinary stone risk in identical twins.

PURPOSE: Quantitative measurements of urinary parameters are valuable clinical tools for predicting the risk of nephrolithiasis. To our knowledge no previous studies have evaluated the heritability of urinary stone risk in identical twins. Because these individuals share identical genetics, the R defined by their phenotypic data are theoretically equal to the entire population H2. MATERIALS AND METHODS: A total of 12 sets of healthy homozygous twins, including 4 males and 8 females for a total of 24 individuals, with a mean age of 25.9 years (range 21 to 36) volunteered for this study. All subjects provided informed written consent before assessment. Urinary stone risk profiles were done elsewhere on 2 consecutive days after 5 days of a standardized diet (170 mEq Na and 2500 kcal). Linear regression was performed on the data to determine R. Because identical twins were used, R was theoretically an estimate of H2. RESULTS: Certain urinary stone risk markers were highly heritable, including urinary calcium (94%), oxalate (94%), citrate (95%), uric acid (96%) and brushite supersaturation (90%), as determined by genotype (H2 90% or greater). Uric acid supersaturation (58%) and urinary sodium (64%) had low degrees of heritability. CONCLUSIONS: H2 is a measure of how much of the total variance in phenotype results from differences in genotype, as opposed to environmental differences. For example, an H2 of 95% for citrate suggests that genetic differences account for 95% of the variation in urinary citrate and environmental differences account for the remaining 5%. Therefore urinary calcium, oxalate and citrate are primarily determined by genotype, while environmental factors, particularly those that impact urine pH and urinary volume, may be increasingly important for determining uric acid supersaturation.

Adult↗
PubMed2006

Renal stone risk in a simulated microgravity environment: impact of treadmill exercise with lower body negative pressure.

PURPOSE: Prolonged exposure to microgravity during spaceflight causes metabolic changes that increase the risk of renal stone formation. Studies during the Gemini, Apollo, Skylab and Shuttle missions demonstrated alterations in renal function, fluid homeostasis and bone resorption that result in increased urinary supersaturation of calcium oxalate, brushite, sodium urate and uric acid. Developing countermeasures to increased urinary supersaturation is an important priority as the duration of space missions increases. MATERIALS AND METHODS: A total of 11 sets of identical twins remained on 6-degree head down, tilt bed rest for 30 days to simulate prolonged microgravity. One twin per pair was randomly selected to exercise while supine in a lower body negative pressure chamber 6 days weekly for 40 minutes, followed by 5 minutes of resting lower body negative pressure at 50 mm Hg. The other twin served as a nonexercise control. Pressure in the exercise lower body negative pressure chamber (52 to 63 mm Hg) was adjusted to produce footward forces equivalent to those for upright running on Earth at 1.0 to 1.2 x body weight. Pre-bed rest urinary stone risk profiles were done elsewhere after 5 days of a standardized diet, consisting of 170 mEq sodium, 1,000 mg calcium, 0.8 gm/kg animal protein and 2,500 kcal, and then throughout the bed rest and recovery phases of the protocol. RESULTS: A significant increase in urinary calcium after just 1 week of bed rest was noted in the nonexercise control group (p = 0.001). However, no such increase was noted in the exercise group. Brushite supersaturation increased significantly from bed rest in each group, although the increase was significantly higher in the nonexercise control group than in the exercise group (p = 0.006). Calcium oxalate supersaturation increased during bed rest in the exercise group (p = 0.004). It trended toward a higher level in the nonexercise control group, although this did not achieve significance (p = 0.055) Mean urine volume +/- SD was significantly higher in the nonexercise control group than in the exercise group at bed rest week 2 and at week 3 (2.01 +/- 0.21 vs 1.63 0.18 l and 2.03 +/- 0.22 vs 1.81 +/- 0.20, respectively). Urinary pH was significantly higher in the nonexercise control group than in the exercise group at week 1 and week 3 (6.62 +/- 0.7 vs 6.49 +/- 0.5 and 6.58 +/- 0.6 vs 6.49 +/- 0.8, respectively, p = 0.01). CONCLUSIONS: Bed rest significantly alters the urinary environment to favor calculous formation. Lower body negative pressure chamber treadmill exercise offers some protection against increases in stone risk during simulated microgravity, particularly with regard to the risks of hypercalciuria and brushite stone formation. The use of lower body negative pressure to augment aerobic exercise in space may decrease the risk of stone formation in astronauts. Adjunct measures, including aggressive hydration and alkalinization therapy, should be considered.

Adult↗
PubMed2006

Durability of flexible ureteroscopes: a randomized, prospective study.

PURPOSE: We performed a randomized, prospective, multi-institutional study evaluating the durability of commercially available flexible ureteroscopes. MATERIALS AND METHODS: A total of 192 patients were randomized to the use of 7 less than 9Fr flexible ureteroscopes, including the Storz 11274AA and Flex-X, the ACMI DUR-8 and DUR-8 Elite, Wolf models 7330.170 and 7325.172, and the Olympus URF-P3. Information about total and lower pole use time, the number and method of ureteroscope insertion, and they type and duration of accessory instrumentation was recorded. Surgeons were asked to rate the visibility and maneuverability of the instrument on a scale of 0-poor to 10-excellent. RESULTS: The indication for ureteroscopy was upper tract calculi in 87% of cases. Of ureteroscope insertions 97% were performed through an access sheath. The average of number of cases before repair ranged from 3.25 for the Wolf 7325 to 14.4 for the ACMI DUR-8 Elite. Average ureteroscope operative time was statistically longer for the DUR-8 Elite (494 minutes) than for the Flex-X (p = 0.047), and the Wolf 7325 and 7330 (p = 0.001 and 0.001, respectively). Duration of use before repair for the URF-P3 (373 minutes) was statistically longer than for the Wolf 7325 and 7330 (p = 0.016 and 0.017, respectively). Minutes of use with an instrument in the working channel were significantly more with the DUR-8 Elite and the URF-P3 than the Wolf 7330 (p = 0.017 and 0.008) and 7325 (p = 0.012 and 0.005, respectively). The ureteroscope that experienced the greatest average duration of lower pole use was the URF-P3, while the shortest was the Wolf 7325 (103 vs 20 minutes, p = 0.005). Average minutes of laser use before breakage was significantly longer for the DUR-8 Elite than for the Wolf 7325 (110 vs 21 minutes, p = 0.021) and 7330 (24 minutes, p = 0.025). CONCLUSIONS: Currently available less than 9Fr flexible ureteroscopes remain fragile instruments. The DUR-8 Elite and Olympus URF-P3 proved to be the most durable devices.

Equipment Design↗
PubMed2006

Case report: the stone-basket nidus.

A 55-year-old man presented with intermittent right-flank pain 6 months after ureteroscopic stone extraction with holmium laser lithotripsy. A distal-ureteral stone was removed that contained fragments of a stone basket. Diligent inspection of endourologic accessories is critical to ensuring no fragments are left in patients, especially when a laser has been used.

Flank Pain↗
PubMed2006

A new spin on the entrapped ureteral calculus.

We describe ureteroscopic lithotripsy using a revolving 1.5F tipless basket. After passing a laser fiber alongside the basket and performing lithotripsy, one uses a rotary wheel at the base of the basket handle to spin the stone to a different area for further fragmentation. This allows complete stone fragmentation, in contrast to traditional laser baskets, which bore a hole through the center of the stone. Irrigation flow testing demonstrated significant advantages with the 1.5F basket with or without a laser fiber alongside the basket compared with traditional baskets.

Equipment Design↗
PubMed2006

Spondyloarthropathy: an independent risk factor for kidney stones.

PURPOSE: To better stratify risk and to verify previous prevalence reports, we conducted a retrospective cohort study comparing the lifetime incidence of nephrolithiasis in patients with spondyloarthropathies (SpA) and rheumatoid arthritis (RA). PATIENTS AND METHODS: Patients with SpA or rheumatoid factor-positive RA were identified from the rheumatology clinics of two Veterans Affairs hospitals and the University of Minnesota. Among them, 168 were confirmed to meet the American College of Rheumatology criteria and gave informed consent to participation. They were sent a survey regarding their rheumatologic diagnosis, coexistent conditions, medications, and history of kidney stones. Of the total, 143 patients responded and met the criteria for analysis. Rheumatoid arthritis patients were age and sex matched with SpA patients as controls. RESULTS: Populations were similar in all categories except that RA patients were more likely to have used prednisone (P < 0.001), bisphosphonates (P < 0.001), and calcium supplementation (P = 0.03). Kidney stones were reported by 23 (29.11%) of the 79 SpA patients compared with 8 (12.5%) of the 64 RA patients (chi (2) = 5.75; P = 0.025). Subgroup analysis of self-reporting stone history in 85 patients was found to be reliable on imaging review (sensitivity 82%; specificity 100%). CONCLUSIONS: Self-reporting of kidney stones by patients is a reliable measure. Despite adjusting for medication use and matching two similar arthritic populations, patients with SpA had a higher incidence of kidney stones than those with RA. This finding suggests that SpA is an independent risk factor for nephrolithiasis. Future studies will evaluate urinary risk factors and polymorphisms in the ANKH gene that may predispose to stone formation in this high-risk group.

Aged↗
PubMed2006

Angiomyofibroblastoma-like tumors (cellular angiofibroma).

Angiomyofibroblastoma-like tumor (cellular angiofibroma) is a rare, circumscribed, slow-growing mesenchymal tumor that occurs predominantly in the vulva, perineum, and pelvis of women. We report two cases of this tumor in men arising as paratesticular masses of the scrotum, summarize the history of this tumor, and discuss why efforts should be made to differentiate it from aggressive angiomyxoma. Recommended treatment is complete surgical excision with long-term follow up exams, as local recurrence may occur many years after resection of the lesion.

Adult↗
PubMed2006

Medical devices used for ureteroscopy for renal calculi.

Urinary stone disease is a problem as old as human civilization. In this article, a brief history of stone disease and the current status of urinary stone disease treatment will be discussed. This review will focus primarily on the newest technology and devices associated with flexible ureteropyeloscopy for the treatment of upper tract urinary stones. In addition to defining the cutting-edge technology that is newly available, this review will glimpse at what technologic advances are expected in the near future. Reference articles that do a good job of defining the current state of flexible ureteropyeloscopy technology and urinary stone disease treatment will be highlighted, along with a reiteration of the major points of the article.

Animals↗
PubMed2005

How do residents manage personal finances?

BACKGROUND: We examined three research questions: How do residents' debts and savings compare to the general public? How do surgical residents' financial choices compare to other residents? How may institutions help residents' personal financial decisions? METHODS: The Survey of Consumer Finances was modified and piloted tested to elicit financial information. The instrument was completed by 612 residents at 8 programs. RESULTS: Only 60% of residents budgeted expenses, and 25% and 10% maintained cash balances <611 dollars and unpaid credit card balances >10,000 dollars, respectively. Compared with controls, residents held greater median ratios of debt to household income (2.46 vs. 1.06, P <0.0001), fewer assets to income (0.64 vs. 2.28, P <0.0001), less net wealth to income -1.43 vs. 0.90, P <0.0001), and lower retirement savings balance to household income (0.01 vs. 0.12, P <0.0001). Surgery residents were the least financially conservative group. Mean annual resident contributions to retirement accounts were $1532 higher at institutions with versus without retirement plans (P <0.01). CONCLUSIONS: Resident debts are higher and savings lower than the general public. This behavior is most common among surgery residents. Residents save more for retirement when they are eligible for tax-deferred retirement plans. Graduate medical programs should instruct residents on financial management.

Adult↗
PubMed2005

Medial thigh pain: neurology or urology?

Flank pain, irritative urinary symptoms, and hematuria are traditional symptoms of urolithiasis. We report a case of urolithiasis in a neobladder in a patient with a chief complaint of medial thigh pain.

Adult↗
PubMed2005

Percutaneous nephrostomy catheters: drainage flow and retention strength.

OBJECTIVES: To evaluate the impact of percutaneous nephrostomy catheter configuration on drainage flow and retention strength. METHODS: The Cook nephrostomy 16F (symmetric balloon), Bardex Council 16F (eccentric balloon), Microvasive Flexima 14F (pigtail), and Bardex Malecot 16F (flange) nephrostomy catheters were attached to an artificial renal pelvis (12-in.-round latex balloon). The balloon was subsequently filled with either 60 mL of water or orange juice with pulp, and gravity drainage of this fluid was recorded as flow into a flowmeter. Using a Force Five Model FDV-100 force gauge, the retention strength was tested by measuring the force required to pull the nephrostomy catheter through an 8-mm hole in a 35-mm-thick biologic tissue specimen (bologna). RESULTS: The maximal flow rate using both orange juice and saline was significantly greater for the Cook nephrostomy than for the Microvasive Flexima, Bardex Malecot, and Bardex Council catheters (P < or = 0.016). The average flow rate using saline for the Cook nephrostomy catheter was significantly greater than for all other catheters (P < or = 0.02) and was significantly greater than for the Microvasive Flexima and the Bardex Council catheters (P < or = 0.036) using orange juice. The retention strength was strongest for the Cook nephrostomy catheter (3.41 +/- 0.14 lb) compared with the Bardex Council (1.75 +/- 0.1), Microvasive Flexima (1.35 +/- 0.3), and Bardex Malecot (0.29 +/- 0.03) catheters. In addition, the Microvasive Flexima catheter resulted in greater maceration of the biologic tissue after forceful dislodgement. CONCLUSIONS: The results of this study have demonstrated that the Cook nephrostomy catheter combines strong drainage flow and strong retention strength during in vitro testing. Clinical evaluations of the ease of use and patient comfort are warranted.

Biophysical Phenomena↗
PubMed2005

Minimally invasive therapy for benign prostatic hyperplasia: practice patterns in Minnesota.

BACKGROUND AND PURPOSE: Benign prostatic hyperplasia (BPH) affects more than 50% of men by the age of 60 and 90% by age 85. Many of these men are not candidates for surgical procedures such as transurethral resection of the prostate (TURP), stimulating the development of less-invasive forms of therapy. We studied the utilization of these newer therapies by urologists practicing in Minnesota. MATERIALS AND METHODS: An anonymous questionnaire was sent to 174 members of the Minnesota Urological Society, of which 58 were available for analysis. A case scenario was presented of a patient with BPH refractory to medical therapy. The options were traditional and minimally invasive therapies. The physician was asked to select whether he or she would offer each option and perform the procedure or refer the patient within or outside the practice. Statistical analysis was performed using chi-square and two-sample t-tests on Minitab software. The results were considered significant at P < 0.05. RESULTS: While 59% of the respondents would offer both minimally invasive and traditional alternatives, 10% would offer only minimally invasive therapy, while 29% would offer only traditional therapy (P = 0.01). The most common minimally invasive therapies offered were transurethral microwave thermotherapy and (55%) and transurethral needle ablation (33%). If they offered a form of minimally invasive therapy, the majority of respondents would perform the procedure themselves. Rural urologists were less likely to offer minimally invasive therapy (43%) than metro physicians (81%; P = 0.035). There was no significant difference in the use of minimally invasive therapies by rural and urban urologists (P = 0.409) or urban and metropolitan urologists (P = 0.119). Urologists completing their training between 1960 and 1980 were less likely to offer minimally invasive therapy. There was no significant difference in the likelihood of offering traditional versus minimally invasive alternatives according to the percent of managed care in the practice. CONCLUSIONS: Urologists closer to the completion of their residency training are more likely to include a minimally invasive technique in their treatment plan, while urologists practicing in rural Minnesota are less likely to offer minimally invasive procedures. Further emphasis should be placed on increasing the availability of minimally invasive techniques in rural settings.

Age Factors↗