Biomedical subjects

C A Peters

Publications and source records attributed to C A Peters.

At least 73 records · Page 4Linked to original sources

PubMed1997

The sonographic diagnosis of infravesical obstruction in children: evaluation of bladder wall thickness indexed to bladder filling.

PURPOSE: The pathophysiological changes that result from posterior urethral valves depend primarily on the degree and duration of infravesical obstruction. Delayed diagnosis may result in progressive bladder dysfunction, renal parenchymal loss or sepsis. Specific radiographic and clinical criteria predictive of a diagnosis of infravesical obstruction are available in the form of voiding cystourethrography and cystoscopy. However, these modalities share the disadvantage of being invasive in nature. Although noninvasive, sonographic evaluation of bladder thickness has a high degree of variability and it markedly depends on the degree of bladder filling. MATERIALS AND METHODS: Bladder wall thickness and bladder diameter were assessed in 15 children with posterior urethral valves, and 10 age and sex matched children with no bladder dysfunction. Ultrasound was performed before intervention (that is catheter placement or valve ablation). RESULTS: A positive predictive value of 93% was achieved between the 2 groups when bladder wall thickness was indexed to inner wall diameter in the anteroposterior or transverse dimension. Mean bladder wall thickness divided by mean inner bladder diameter plus or minus standard deviation was 0.402 +/- 0.25 in the obstructed population and 0.094 +/- 0.025 in controls (p = 0.0004). CONCLUSIONS: The bladder thickness index is a sensitive sonographic predictor of infravesical obstruction. Application of this index as a noninvasive screening tool for the patient with persistent voiding dysfunction may prove beneficial for identifying infravesical pathology.

Child↗

PubMed1997

Pediatric Vesicoureteral Reflux Guidelines Panel summary report on the management of primary vesicoureteral reflux in children.

PURPOSE: The American Urological Association convened the Pediatric Vesicoureteral Reflux Guidelines Panel to analyze the literature regarding available methods for treating vesicoureteral reflux diagnosed following a urinary tract infection in children and to make practice policy recommendations based on the treatment outcomes data insofar as the data permit. MATERIALS AND METHODS: The panel searched the MEDLINE data base for all articles from 1965 to 1994 on vesicoureteral reflux and systematically analyzed outcomes data for 7 treatment alternatives: 1) intermittent antibiotic therapy, 2) bladder training, 3) continuous antibiotic prophylaxis, 4) antibiotic prophylaxis and bladder training, 5) antibiotic prophylaxis, anticholinergics and bladder training, 6) open surgical repair and 7) endoscopic repair. Key outcomes identified were probability of reflux resolution, likelihood of developing pyelonephritis and scarring, and possibility of complications of medical and surgical treatment. RESULTS: Available outcomes data on the various treatment alternatives were summarized in tabular form and graphically, and the relative probabilities of possible outcomes were compared for each alternative. Treatment recommendations were based on scientific evidence and expert opinion. The panel concluded that only a few recommendations can be derived purely from scientific evidence of a beneficial effect on health outcomes. CONCLUSIONS: For most children the panel recommended continuous antibiotic prophylaxis as initial treatment. Surgery was recommended for children with persistent reflux and other indications, as specified in the document.

Child↗

PubMed1997

Increased renal echogenicity: a sonographic sign for differentiating between obstructive and nonobstructive etiologies of in utero bladder distension.

PURPOSE: The combination of in utero bladder distension and bilateral hydroureteronephrosis in male fetuses may result from a number of pathological processes. The prenatal and postnatal treatment of patients with an enlarged bladder is dictated by the specific etiology leading to these changes. We propose specific ultrasonographic criteria for differentiating between obstructive and nonobstructive etiologies in these fetuses. MATERIALS AND METHODS: We reviewed the medical records and prenatal imaging studies of 18 cases of marked in utero bladder distension in which a diagnosis of posterior urethral valves, the megacystis-megaureter association or the prune-belly syndrome was confirmed postnatally. Amniotic fluid volume and renal echogenicity were assessed before knowledge of the specific diagnosis. Oligohydramnios was graded as mild, moderate or severe. Increased renal echogenicity was defined as greater echogenicity of the renal cortex and/or medulla than of adjacent liver tissue. Postnatal imaging, clinical course and outcome were also reviewed. RESULTS: The study included 15 cases with adequate followup, including 8 in which a diagnosis of posterior urethral valves was confirmed postnatally. Nonobstructive etiologies included the megacystis-megaureter association in 6 cases and the prune-belly syndrome in 1. Seven of the 8 patients with posterior urethral valves had moderate to severe oligohydramnios, whereas all but 1 with a nonobstructive etiology had normal amniotic fluid. Seven of the 8 cases with posterior urethral valves had a marked bilateral increase in renal echogenicity, while none of the nonobstructive cases had this finding. CONCLUSIONS: Increased renal echogenicity and oligohydramnios in the setting of bladder distension are highly predictive (87%) of an obstructive etiology. This finding is important in the prenatal counseling and treatment of boys with bilateral hydronephrosis and marked bladder dilatation.

Diagnosis, Differential↗

PubMed1996

A demographic study of polydipsia in an institution for the intellectually disabled.

OBJECTIVE: To measure the prevalence of primary polydipsia in an Ontario institution for residents with developmental disabilities and to explore the associations of polydipsia with age, sex and level of mental retardation. METHOD: All 798 residents were screened for polydipsia using a behavioural questionnaire completed by caregivers. RESULTS: Thirty-three cases were detected: the prevalence among the mobile resident population (n = 660) was 5%. We found no association of polydipsia with age, sex, or level of mental retardation. CONCLUSIONS: Physicians should be aware of polydipsia because it is common among residents with moderate, severe, and profound mental disability. Unless screened for specifically, polydipsia may go unrecognized and may place the residents with mental handicap at risk for serious acute and chronic complications.

Adult↗

PubMed1996

Screening patients with mental retardation for polydipsia.

OBJECTIVES: To determine whether caregiver responses to a screening question are a reliable method of identifying polydipsia (excessive water drinking) in institutionalized residents with mental retardation. To review the etiology, acute and chronic clinical manifestations, and care of polydipsia and water intoxication. METHOD: This paper presents an assessment of interrater reliability for a screening question for polydipsia using responses of primary caregivers of preidentified polydipsia cases (n = 32) and matched controls (n = 33) in a large Canadian institution for developmentally handicapped adults. A chart review of all cases of identified water intoxication is also provided. The behavioural outcomes of preventive measures for water intoxication are described. RESULTS: The screening instrument was reliable, having a kappa (interrater reliability) of 0.73. Several case descriptions illustrate typical presentations of water intoxication in this population. CONCLUSIONS: Polydipsia is reliably identified by caregiver responses to a screening question. It should be screened for regularly to ensure appropriate care to prevent important acute and chronic complications.

Adult↗

PubMed1996

Complications in pediatric urological laparoscopy: results of a survey.

PURPOSES: To assess the level of activity in pediatric urological laparoscopy and its relationship to complications a survey of the membership of the American Academy of Pediatrics, Section on Urology was conducted. MATERIALS AND METHODS: An anonymous questionnaire was mailed to 251 pediatric urologists and 153 responses were recorded. RESULTS: Of the respondents 75% reported performing diagnostic and operative laparoscopy (average 54 cases). Patient age ranged from newborn to 20 years. Average case load for laparoscopy was 19 of 401 total cases yearly. More than 5,400 laparoscopic cases are represented by the reported experience. Complications were reported in 5.38% of cases (average complication rate 6.06% per practitioner). Excluding preperitoneal insufflation or subcutaneous emphysema the complication rate was 1.18%. Complications requiring surgical repair occurred in 0.39% of cases, including bowel, bladder and great vessel injury. The clearest predictor of complication rate was laparoscopic experience. The technique used to obtain pneumoperitoneum was also important in that Veress needle technique was associated with a 2.6% significant complication rate in contrast to 1.2% for open technique (p < 0.006). CONCLUSIONS: Laparoscopy is widely practiced in the pediatric urological community with a good safety record. Complications occur and important means of minimizing them are to provide for supervised experience with emphasis on the details of safe technique.

Child↗

PubMed1996

Reconstructive options in genitourinary rhabdomyosarcoma.

PURPOSE: We attempted to develop a rational and consistent scheme for surgical reconstruction in patients with genitourinary rhabdomyosarcoma. MATERIALS AND METHODS: We reviewed the records of 35 patients with resectable genitourinary rhabdomyosarcoma treated from 1970 to 1993. RESULTS: Primary sites included bladder in 11 cases, prostate in 13, vagina/uterus in 9 and pelvic tumors of uncertain origin in 2. A total of 33 patients underwent surgery, including partial and radical cystectomy in 17 (bowel conduit diversion in 10, continent urinary diversion in 6 and ureterosigmoidostomy in 1). Overall 30 of the 33 surgical patients are free of disease 4 months to 24 years after diagnosis. CONCLUSIONS: A nonrefluxing colon conduit is appropriate at cystectomy. Continent diversion fashioned from the original conduit may be planned as the patient achieves a durable disease-free status.

Adolescent↗

PubMed1996

Laparoscopy in pediatric urology: challenge and opportunity.

The development of operative laparoscopic techniques in Pediatric Urology has been generally cautious. It is premature to attempt an assessment of the ultimate impact of laparoscopy in pediatric urology, yet several areas of application have significant potential. Diagnostic laparoscopy for cryptorchidism has evolved into operative laparoscopy for intra-abdominal testes, and a significant number of cases have been performed successfully, with the possibility of improved results over open techniques. Laparoscopic nephrectomy and nephroureterectomy have been spring-boards for complex reconstructive renal surgery, although it is clear that new tissue joining technologies are needed. Complex reconstructive surgery is just beginning, yet may have a role in practice. These developments and the current status of laparoscopy in pediatric urology will be reviewed.

Child↗

PubMed1995

Congenital bladder obstruction: research strategies and directions.

The clinical significance of congenital bladder obstruction is evident to those who deal with children suffering from severe bladder dysfunction and renal failure. It is a lifelong effect often requiring complex surgical reconstruction and renal transplantation. CBO also represents an important pathophysiologic process with relevance to other organ systems in which hypertrophic and fibrotic processes occur. CBO occurs in a dynamic and developing organ in which function and development are interdependent. Alterations of one will induce alterations in the other which then affect the first. Multiple levels of organization are involved and relevant, from the cell to the whole bladder as a part of the organism. Functional and developmental changes have been demonstrated in models of CBO. Much attention has been focused on the connective tissue compartment of the bladder due to its important role in determining bladder compliance characteristics. Preliminary findings suggest that connective tissue remodeling may be affected by alterations in the balance of the regulatory mechanisms of collagen degradation. Further studies should be able to define these alterations and may permit specific modulation of these mechanisms.

Animals↗

PubMed1995

Peptide-derived transition state analogue inhibitors of thrombin; synthesis, activity and selectivity.

In a study to combine the transition state analogue concept with the principle of catalytic site spanning, a series of peptide-derived transition state analogue (TSA) inhibitors of thrombin has been synthesized and tested. In the sequence H-D-Phe-Pro-Arg-Gly-OH (2) the Arg-Gly amide bond has been replaced by three classes of transition state analogues, being the ketomethylene, the hydroxyethylene and the hydroxymethylene amide bond replacements. Compound 12a, in which the amide bond has been replaced by the ketomethylene group, was found to be the most potent thrombin inhibitor of the series studied. Subsequently, penta- and hexapeptide sequences with good affinity for thrombin were developed, i.e. H-D-Phe-Pro-Arg-Gly-Phe-OH (16) and H-D-Phe-Pro-Arg-Gly-Phe-Lys-OH (26). In these sequences the Arg-Gly amide bond was then replaced by the ketomethylene group. The resulting compounds 43a and 47a, respectively, were evaluated in vitro as inhibitors of thrombin and factor Xa. Compound 47a was found to be the most potent thrombin inhibitor of the series studied (Ki = 29 nM). The combination of the transition state analogue concept and the principle of peptide elongation (tetrapeptide-->hexapeptide) yields thrombin inhibitors of high potency and selectivity. The effects of these two alterations reinforce each other indicating a synergistic effect. This might be rationalized by entropy factors.

Amino Acid Sequence↗

PubMed1995

Urinary tract obstruction in children.

PURPOSE: Perinatal identification of children with congenital urinary obstruction has challenged our understanding of the pathophysiology and clinical treatment of many children with hydronephrosis. MATERIALS AND METHODS: A critical review of recent reports relating to congenital urinary obstruction in children was performed in an attempt to integrate clinical and experimental information. RESULTS: Several themes emerged from the many reports relating to congenital urinary obstruction that have not been previously emphasized. Congenital obstruction begins and evolves in a developing fetal kidney, indicating the importance of the effect of obstruction on renal growth and development, which is distinct from the postnatal renal response to obstruction. Variation in the ability of the developing kidney to compensate for obstruction may be an important factor in explaining variability in clinical and experimental reports. Clinical data show an unpredictable outcome of congenital hydronephrosis. Nonoperative management of hydronephrosis is supported by empirical evidence yet raises many questions regarding the certainty of outcome and the risks involved. It imposes on the practitioner a significant clinical obligation. The ability to differentiate between clinically significant and insignificant obstruction is the current challenge to be fulfilled by integrated clinical and experimental investigation. CONCLUSIONS: The unique features of congenital urinary obstruction separate it from better understood acquired postnatal obstruction. Understanding the effects of obstruction on the developing kidney prenatally and postnatally is critical. A definition is proposed for congenital urinary obstruction in children, that is a condition of impaired urinary drainage which, if uncorrected, will limit the ultimate functional potential of a developing kidney.

Animals↗

PubMed1995

Comparative urodynamics of appendiceal and ureteral Mitrofanoff conduits in children.

We report the cystometric and conduit pressure profilometric findings of 20 children for whom the Mitrofanoff principle was applied to the construction of 21 continent catheterizable urinary conduits. Mitrofanoff conduits were fashioned from ureter in 10 cases, appendix in 8, ileum in 1, stomach in 1 and a combination appendix and ureter in 1. Conduit pressure profiles showed that functional profile length correlated strongly with the static profile maximal Mitrofanoff closure pressure (p = 0.04) and dynamic profile maximal Mitrofanoff closure pressure (p = 0.02). There was a statistically significant difference between clinical continence rates for children above and below the functional profile length threshold of 2.0 cm. (p = 0.05). The zone of continence corresponded to the region of the conduit intramural tunnel. Only 2 of 21 conduits were incontinent but both were constructed with ureters implanted into bowel reservoirs. Compared to appendiceal conduits, ureteral conduits had a lower functional profile length (p < 0.01) and static profile maximal Mitrofanoff closure pressure (p < 0.01), indicating a possible advantage to the use of the appendix.

Adolescent↗

PubMed1995

The long-term urological response of neonates with myelodysplasia treated proactively with intermittent catheterization and anticholinergic therapy.

PURPOSE: Urinary tract management in children with myelodysplasia is controversial. Some advocate observation alone, while others believe that the prophylactic institution of intermittent catheterization and anticholinergic therapy may help to prevent deterioration. MATERIALS AND METHODS: A nonrandomized prospective study was instituted to compare the urological outcomes of a cohort of children who were at risk for urological deterioration on the basis of bladder-sphincter dyssynergia and/or high filling or voiding pressures. Those at risk were observed until deterioration occurred, or were placed on prophylactic intermittent catheterization with or without anticholinergic medication. RESULTS: Of 44 children at risk 35 followed by observation alone had urinary tract deterioration, whereas only 3 of 20 at risk treated with prophylactic intermittent catheterization had deterioration with time. CONCLUSIONS: Proactive bladder treatment significantly reduced the incidence of upper urinary tract deterioration and need for surgical intervention.

Cholinergic Antagonists↗

PubMed1995

Pediatric laparoscopic dismembered pyeloplasty.

We performed laparoscopic dismembered pyeloplasty in a boy with right ureteropelvic junction obstruction using 4 cannula sites, and a dismembering and reanastomosis technique identical to that used in open pyeloplasty. Interrupted sutures were placed and tied intracorporeally. A nephrostomy tube was placed under direct vision for drainage but no ureteral stent was used. Total operating time was 5 hours. The patient was discharged home 36 hours after the procedure. The nephrostomy tube was removed 10 days postoperatively after radiographic demonstration of patency and 24 hours of clamping without pain. Followup excretory urography at 6 weeks showed much less hydronephrosis and a widely patent anastomosis. Our case illustrates the technical features and feasibility of laparoscopic pyeloplasty in children, and should encourage further development of pediatric urological reconstructive laparoscopic techniques.

Child↗

PubMed1995

Prenatal sonographic detection of genital malformations.

Postnatal clinical and pathological correlation of sonographically identified genital malformations in 17 fetuses was undertaken to determine the outcome of these findings. Diagnoses confirmed at autopsy or by postnatal examination and surgery included male (XY) pseudohermaphroditism in 2 cases, hypospadias with chordee in 3, microphallus in 2, cloacal anomaly in 2, congenital adrenal hyperplasia in 3, penoscrotal transposition in 2, intra-abdominal testes in 1, megalourethra in 1 and cloacal exstrophy variant in 1. Additional abnormalities included congenital heart defects, cleft palate, and renal, anorectal, cranial and cerebral malformations. Four fetuses with a sonographically abnormal appearing phallus were found to have an endocrine disorder (3 congenital adrenal hyperplasia and 1 panhypopituitarism). Outcomes included 2 abortions and 1 neonatal death with the remaining neonates undergoing medical and reconstructive treatment. Prenatal detection of genital abnormalities can be helpful in evaluating those fetuses with severe multi-system anomalies as well as lesions more amenable to correlation in the neonatal period. Detection is particularly important in neonates with endocrine disorders, and complex genitourinary and anorectal malformations.

Female↗

PubMed1995

Expression of cell growth regulated genes in the fetal kidney: relevance to in utero obstruction.

Previous studies of fetal urinary tract obstruction (bladder outlet obstruction and ureteral obstruction) in lambs have shown that obstructions created relatively early in gestation (4/10 to 6/10 term) can significantly affect growth of the developing kidney. This suggests that urinary tract obstruction in utero can alter normal mechanisms of kidney growth. However, a mechanism for these effects has not yet been proposed. In this study we have used mRNA expression analysis to characterize the temporal sequence of expression of several growth-regulated genes during normal ovine kidney development. The purpose of this study was to test the hypothesis that early obstructions, such as those believed to arise in congenital obstructive uropathy in humans, might have a disproportionate effect on hyperplastic growth if the cellular growth fraction (percent of cells in the organ undergoing DNA synthesis) was greater in the second trimester than in the last. Northern blot analysis of the cell cycle-dependent genes histone H3, c-myc and ornithine decarboxylase (ODC) indicated a progressive, gradual decline in cellular proliferation in the kidney from approximately 60 to 135 days (4/10 term to term) gestation, as evidenced by decreases in the respective mRNA levels. The greatest levels of cell proliferation occurred near the midpoint of gestation. This indirect measurement of decline in cellular growth fraction was reflected in direct measurements of change in relative kidney weight. To test whether this decline in mRNA levels occurs widely among genes expressed in the fetal kidney during this period, relative expression levels of more than 300 anonymous mRNA transcripts were evaluated by differential display analysis. This method showed that genes whose expression patterns resembled the growth-regulated genes constituted less than 5% of the expressed mRNAs identified. These data indicate that intrauterine urinary tract obstructions that arise at or near the midpoint of gestation coincide with the highest rates of cell proliferation occurring in the second and third trimesters and, therefore, might adversely affect mechanisms of cell proliferation.

Animals↗

PubMed1995

Postoperative adhesion formation after urological laparoscopy in the pediatric population.

The risk of intraperitoneal adhesion formation is a concern with transperitoneal laparoscopic surgery. To evaluate the incidence of adhesions after interventional urological laparoscopy, we reviewed 41 pediatric patients who had undergone second-look procedures. The number of adhesions and quantitation of the degree of each adhesion were assessed. Major laparoscopic procedures were performed previously in 8 patients, moderate in 29 and minor in 4. Adhesions were noted in 4 patients (9.8%), including 2 adhesions at the operative site and 2 at trocar sites. The risk of adhesions increased with the extent of dissection. Two adhesions developed after major procedures but the grade and extent of these adhesions were minimal. In the majority of patients re-peritonealization occurred with minimal or no scarring noted. Although adhesions may occur with pediatric urological laparoscopic procedures, the incidence appears lower than what one would expect with open exploration.

Child↗

PubMed1994

Experimental fetal tracheal ligation reverses the structural and physiological effects of pulmonary hypoplasia in congenital diaphragmatic hernia.

Infants with congenital diaphragmatic hernia (DH) and profound pulmonary hypoplasia are currently unsalvageable. The authors previously demonstrated that tracheal ligation (TL) accelerates fetal lung growth and reverses the pulmonary hypoplasia of fetal nephrectomy. The purpose of this study was to determine if the pulmonary hypoplasia of experimental DH could be similarly reversed and, if so, whether the resulting lungs would show better function than those of their DH counterparts. Eighteen fetal lambs were divided into three experimental groups of six animals each. In group 1, DH was created at 90 days' gestation. In group 2, DH was created at 90 days' gestation and TL performed during the same operation. Group 3 consisted of sham-operated controls. These animals were delivered near full-term, and their lungs analyzed by standard morphometric techniques. Ten additional fetal lambs were divided into two experimental groups of five animals each. In group 4, DH was created at 90 days' gestation. In group 5, DH was created at 90 days' gestation and TL performed 20 days later, at 110 days' gestation. These animals were pressure-ventilated via tracheostomy over a 2-hour period in which PaO2, PaCO2, and compliance were measured. Intratracheal pressure (ITP) was measured at the time of delivery in all groups. Upon retrieval, DH animals had abdominal viscera in the chest and small lungs; in contrast, DH/TL animals had the herniated viscera reduced from the chest by enlarged lungs. DH/TL lungs showed markedly increased growth, with significant increases in lung volume:body weight ratio (LV:BW; P = .0001), alveolar surface area (ALV.SA; P = .0001), and alveolar number (ALV#) (P = .0001) when compared with those of the DH or control group. This growth was associated with a normal maturation pattern based on histological appearance, normal airspace fraction, and normal alveolar numerical density. ITP in the DH/TL group was increased when compared with that of DH and control animals (P = .0001). Total lung DNA and protein were both elevated in the DH/TL animals (P = .0001). However, the DNA:protein ratio remained normal, suggesting lung growth had occurred through cell proliferation, not by hypertrophy. When ventilated over a range of settings, DH/TL lungs were more compliant (P = .0001) and achieved higher PaO2s (P < .003) and lower PaCO2s (P = .0001) than their DH counterparts. From these data, the authors conclude: (1) Experimental fetal DH produces hypoplastic lungs that are not capable of adequate gas exchange with conventional ventilation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗