Biomedical subjects

G A Bogaert

Publications and source records attributed to G A Bogaert.

16 recordsLinked to original sources

PubMed1999

[Preliminary experiences with the use of the Holmium-YAG laser in the treatment of soft tissues and of cystine calculi in children].

INTRODUCTION: Experience of the use of the Holmium: Yttrium-Aluminium-Garnet (Ho:YAG) laser in children has been limited. However, the Ho:YAG laser has been in clinical use in urology for several years but has mainly been used for the treatment of renal stones and benign prostatic hyperplasia. Due to its unique combination of vaporization and coagulation, the Ho:YAG laser allows a precise cutting action. The depth of penetration in water and tissue is limited to < 0.5 mm and therefore provides a safety margin. The Ho:YAG laser can be used in children, as the energy can be delivered via fibers that range from 200 to 1000 mu in diameter. MATERIALS AND METHODS: We used the Ho:YAG laser in 5 children (2-15 years): one child (2 years) with bladder exstrophy had a urethral stricture after bladder neck reconstruction, two children (6 years and 14 years) had ureteropelvic junction (UPJ) stenosis and refused open surgery and two children (5 years and 15 years) suffered from cystine stones (ESWL failed). The urethral stricture was incised in a retrograde fashion. We performed an antegrade incision of the UPJ with the Ho:YAG laser in the 6-year-old child and a retrograde incision in the 14-year-old child. We removed the stones in antegrade fashion in the 5-year-old child and in retrograde fashion in the 15-year-old child. RESULTS: All children now have more than 12 month's follow-up. There were no immediate or late complications. The boy with urethral stricture remained free of recurrence, the boy with UPJ stenosis obtained improved drainage on the excretory renogram and the two children with cystine stones remained stonefree. CONCLUSION: We have shown that the safety and efficacy of the Ho:YAG laser is also reproducible in urologic pathology in children. In addition, due to its vaporizing quality, the Ho:YAG laser is more effective in the treatment of cystine stones and allows minimaly invasive treatment in children.

Adolescent↗

PubMed1997

Hemodynamic changes after complete unilateral ureteral obstruction in the young lamb.

PURPOSE: We studied renal hemodynamic changes after complete acute unilateral ureteral obstruction in the young lamb. MATERIALS AND METHODS: Seven 4-week-old lambs underwent unilateral complete ureteral obstruction and renal blood flow was monitored in both kidneys with ultrasonic flow transducers. Ureteral and arterial blood pressure was measured. RESULTS: In the obstructed kidney renal blood flow was stable for 5 hours and then decreased thereafter to 71% of baseline at 5 days (p < 0.05). In the contralateral kidney the pattern of renal blood flow constituted a mirror image, although the magnitude of the increase was decreased (122% of baseline at 5 days, not statistically significant). Mean arterial blood pressure did not change in 5 days. Mean ureteral pressure increased from a baseline of 9 to 37 mm. Hg (p < 0.001) 2 hours after obstruction but gradually decreased to 24 mm. Hg after 24 hours and remained elevated for 5 days (p < 0.001). CONCLUSIONS: The pattern of renal blood flow and ureteral pressure response to obstruction in the young lamb is different from that previously reported. Renal blood flow does not increase after obstruction and it is relatively preserved at 5 days. This unexpected response may be a result of the compound caliceal sheep kidney, immaturity of the young vascular system or development differences in the mechanism of spontaneous decompression of the collecting system.

Age Factors↗

PubMed1996

Lower urinary tract function in ambulatory children with spina bifida.

OBJECTIVE: To investigate lower urinary tract function in ambulatory children with myelomeningocele. PATIENTS AND METHODS: The urological course of 45 children with myelomeningocele who walked either independently (19 children) or with ankle-foot orthotics (26 children) was reviewed. Follow-up ranged from 9 months to 13.5 years (mean 4.75 years). RESULTS: A normal pattern of voiding was observed both clinically and during urodynamic evaluation in only three of the 45 children, with the remainder displaying neurogenic lower urinary tract dysfunction. The independent walkers and those with orthotics did not differ in the spectrum of lower urinary tract dysfunction or other variables. Those patients with persistent incontinence underwent an initial urodynamic evaluation when older (mean 3.7 years versus 6.4 weeks in those who were continent). CONCLUSION: Ambulatory children with myelomeningocele suffer the full spectrum of lower urinary tract dysfunction. Given the potential danger of untreated lower urinary tract dysfunction, ambulatory children with myelomeningocele should receive the same diagnostic and therapeutic attention as their peers with more overt neurological deficits.

Adolescent↗

PubMed1996

Efficacy of retrograde endopyelotomy in children.

PURPOSE: Endopyelotomy has been performed extensively in adults for the treatment of ureteropelvic junction obstruction. To determine its applicability to the pediatric population we reviewed our experience with retrograde endopyelotomy in children. MATERIALS AND METHODS: Eight children 4 to 15 years old were treated with retrograde endopyelotomy and results were compared to those of a concurrent group of 8 treated with open pyeloureteroplasty. RESULTS: Retrograde endopyelotomy was done in all of our patients with lower ureteral dilatation (as an adjunct measure in 5). Seven patients had symptomatic and radiographic improvement. The patient in whom the procedure failed had a crossing lower pole vessel. Postoperative analgesia, length of hospitalization and cost were lower in the endopyelotomy group. CONCLUSIONS: Retrograde endopyelotomy is feasible in children older than age 4 years and it results in reduced morbidity. The success rate is high but open surgery remains the standard, particularly when a crossing lower pole vessel is identified preoperatively.

Adolescent↗

PubMed1996

Exogenous endothelin-1 causes renal vasodilation in the fetal lamb.

PURPOSE: Endothelin-1 is known to be a potent vasoconstrictor. We investigated the effects and mechanisms of action of endothelin-1 and its receptors in regulating renal vascular tone in the fetal lamb. MATERIALS AND METHODS: We observed the in vivo effects of endothelin-1, an endothelin-b receptor agonist (4-alanine-endothelin-1), endothelin-a receptor antagonists (BQ-610 and BQ-123), and the inhibition of prostaglandin and nitric oxide synthesis on the response of the renal circulation to endothelin-1 in a chronic preparation in third trimester fetal lambs. RESULTS: After injection of 250 ng./kg. endothelin-1 into the descending aorta proximal to the renal arteries in 8 fetal animals, renal blood flow increased (4.4 +/- 0.7 ml. per minute per kg., p < 0.001 versus vehicle), as did mean arterial blood pressure (3.0 +/- 0.3 mm. Hg,p < 0.001 versus vehicle). Calculated renal vascular resistance decreased (-1.1 +/- 0.2 mm. Hg per minute per kg./ml., p < 0.001 versus vehicle). After injection of 1,725 ng./kg. 4-alanine-endothelin-1 in 5 animals renal blood flow increased (3.8 +/- 0.4 ml. per minute per kg., p < 0.05 versus vehicle) and mean arterial blood pressure was unchanged (1.6 +/- 1.7 mm. Hg). Calculated renal vascular resistance decreased (-0.8 +/- 0.2 mm. Hg per minute per kg./ml., p < 0.05 versus vehicle). After injection of 0.5 mg./kg. BQ-610 in 6 animals renal blood flow increased (2.3 +/- 0.7 ml. per minute per kg., p < 0.05) and mean arterial blood pressure decreased (-2.7 +/- 0.3 mm. Hg, p < 0.05 versus vehicle). Calculated renal vascular resistance decreased but this difference was not statistically significant (-0.7 +/- 0.3 mm. Hg per minute per kg./ml., p < 0.07). A dose of 1 mg./kg. BQ-123 in 2 animals decreased renal vascular resistance markedly. Infusion of a prostaglandin synthesis inhibitor (1 mg./kg. per minute meclofenamic acid) did not alter the decrease in renal vascular resistance after endothelin-1 (-0.7 +/- 0.4 mm. Hg per minute per kg./ml). In contrast, during infusion of a nitric oxide synthesis inhibitor (1.5 mg./kg. per minute N-omega-nitro-L-arginine) endothelin-1 increased renal vascular resistance (1.2 +/- 0.2 mm. Hg per minute per kg./ml., p < 0.001). CONCLUSIONS: Endothelin-1 is a vasodilator in the fetal renal circulation, which acts primarily via endothelin-b receptors. Ongoing activity of endothelin-a receptors contributes to renal vascular tone in fetal lambs. The vasodilatory effects of endothelin-1 in the fetal lamb renal circulation are mediated via the nitric oxide system and not via prostanoids.

Animals↗

PubMed1995

Urine concentration and enuresis in healthy preschool children.

OBJECTIVES: To determine whether children concentrate their urine overnight and to assess the correlation between specific gravity of a first morning urine specimen and the results of a questionnaire concerning bedwetting, voiding habits, and continence in 47 healthy children aged 3 to 6 years. DESIGN: A prospective observer-blinded consecutive sample. SETTING: Two San Francisco, Calif., preschools. PARTICIPANTS: Forty-seven children attending preschool during the study period. MEASUREMENTS/MAIN RESULTS: Forty of 47 children had a urine specific gravity greater than 1.020. None of these children wet the bed during this study, although four (11%) of 36 had a history of bedwetting. Furthermore, seven children with a urine specific gravity of 1.015 or lower had a history of bedwetting and wet the bed during this study. A voiding frequency of six or more times per day, by history, was associated with a 3:1 relative risk of bedwetting but did not segregate children with primary enuresis from those with secondary enuresis. CONCLUSIONS: Our results indicate that healthy children aged 3 to 6 years are able to concentrate their urine. In addition, urine specific gravity was an accurate predictor of the presence of nocturnal enuresis in this group of children. Our results suggest that a specific gravity of the first morning urine specimen should be correlated with appropriate history before extensive diagnostic evaluation or empiric therapy is performed in children with nocturnal enuresis.

Child↗

PubMed1995

Renal preservation despite 35 days of partial bladder obstruction in the fetal lamb.

To determine whether the increase in renal blood flow and preservation of renal function that we demonstrated after 10 days of chronic partial bladder obstruction in the third trimester fetal lamb also occur after earlier longer obstruction, we modified our preparation and studied the effects of 35 days of obstruction begun during the second trimester. Partial bladder obstruction was created in 10 fetal lambs at 90 days of gestation (term equals 147 days). At repeat surgical intervention 28 days later vascular catheters and a left renal artery flow transducer were placed, and catheters were externalized. We then studied renal blood flow and function at gestational ages 120 days and 125 days after 30 days and 35 days of obstruction, respectively. Tissue was obtained for histology at the time of sacrifice. Eight control fetal lambs without obstruction were studied in a similar way. Bilateral hydroureteronephrosis was noted in all fetal lambs after partial obstruction, whereas the kidneys and bladders of the control animals had a normal appearance. Renal blood flow was higher in the obstructed fetal lambs than in controls (20.2 +/- 4.9 versus 10.2 +/- 0.9 ml. per minute per kg., p < 0.05 after 30 days and 17.1 +/- 2.7 versus 9.7 +/- 0.9 per minute per kg., p < 0.05 after 35 days). There was no evidence of decreased renal function by any parameter and, in fact, glomerular filtration rate and urine volume were increased after 30 days of obstruction (1.59 +/- 0.32 versus 0.69 +/- 0.07 ml. per minute per kg., p < 0.05 and 15.7 +/- 4.3 versus 5.2 +/- 0.8 ml. per hour per kg., p < 0.05, respectively). Histological studies demonstrated normal architecture of the kidneys but thinned cortex. We conclude that the physiological responses of the fetus are such that partial lower urinary tract obstruction in our preparation results in a prolonged increase in renal blood flow and preservation of renal function.

Animals↗

PubMed1995

Contradictory renal function measured with mercaptoacetyltriglycine diuretic renography in unilateral hydronephrosis.

PURPOSE: We studied apparently supranormal renal function in hydronephrotic kidneys, as measured by 99mtechnetium mercaptoacetyltriglycine renography. MATERIALS AND METHODS: We retrospectively reviewed the clinical history, ultrasonography and renography of 29 children. RESULTS: Of the 29 children 7 had greater than 50% relative function in the hydronephrotic kidney. This finding was independent of patient age, gender, degree of hydronephrosis or obstructive pattern. Of these 7 cases 6 occurred on the right side (p < 0.05 versus a large registry). CONCLUSIONS: In most cases supranormal renal function is caused by a technical problem, likely the inadequate background subtraction of mercaptoacetyltriglycine in the liver.

Child↗

PubMed1995

The physiology of gastrocystoplasty: once a stomach, always a stomach.

To determine the physiology of acid secretion after gastrocystoplasty with the body of the stomach we performed a prospective standardized 3-day study in 13 children (median age 12.5 years) who had undergone bladder augmentation/replacement (median postoperative period 2 years). Urinary pH and titratable acid, and serum gastrin levels were measured after gastric distention with a meal and bladder distention with urethral filling at baseline and after medication with a histamine-2 receptor antagonist or an anticholinergic agent. Five children underwent cystoscopy and biopsy of the gastric and native segments of the gastrocystoplasty. In the fasting state pH was neutral, there was no titratable acid in the urine and serum gastrin level was normal in all cases. After a meal urinary acid secretion and serum gastrin level increased markedly. After each medication half of the patients demonstrated marked inhibition of urinary acid secretion after a meal while response was partial in the remainder. In none of the patients was there significant alteration in the pattern of gastrin secretion. Bladder distention did not result in urinary acid secretion or gastrin secretion. The cystoscopic and histological appearance of the native bladder and stomach segment of the gastrocystoplasty in the 5 patients was normal. We conclude that the gastric body segment used in gastrocystoplasty continues to secrete acid as though it were part of the stomach. The secretion of acid in the urine can be decreased with histamine-2 receptor antagonist or anticholinergic medication.

Adolescent↗

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

Role of nitric oxide in fetal lower urinary tract function.

We studied the role of nitric oxide (NO) in normal function of the lower urinary tract in fetal lambs. Fetal surgery was performed in pregnant ewes at 118 days' gestation (term 145-days) to place arterial, venous, and double-lumen urachal catheters. Five animals had a catheter secured in the distal urethra (to measure voided volume), and six underwent ligation of the urethra. Urodynamic studies were performed via the urachal catheter under baseline conditions, during systemic blockade of NO synthesis with N omega-nitro-L-arginine, and with systemic NO stimulation by L-arginine 48 hours postoperatively. Nitric oxide blockade caused an 88% mean increase in bladder capacity (volume to initiation of voiding) (p < 0.001) and a 5.8-fold increase in mean postvoid residual volume (p < 0.0001) despite normal maximal bladder pressures, suggesting inadequate sphincteric relaxation. Qualitatively, NO inhibition increased the presence of low-level bladder contractions and caused a trend toward decreased bladder compliance. Increase of NO substrate by L-arginine infusion restored baseline findings if performed after N omega-nitro-L-arginine. Stimulation of NO by L-arginine infusion caused continuous efflux of the infusate secondary to a persistently open sphincter. In conclusion, NO is active in the function of the lower urinary tract in the fetal lamb and appears to influence both sphincter and detrusor activity.

Animals↗

PubMed1994

Renal hemodynamic and functional effects of 10 days' partial urinary obstruction in the fetal lamb.

We studied fetal lambs to define the renal pathophysiology of chronic in utero partial bladder outlet obstruction. These fetal lambs, 115 to 120 days gestation (term = 145 days), underwent urethral ligation, placement of a urachal catheter and positioning of an ultrasonic flow transducer around the left renal artery. Partial obstruction was created by placing a narrow connector between the urachal and an amniotic catheter. In control animals a large connector was placed to allow free drainage of the bladder into the amniotic cavity. Renal blood flow was measured daily, and urine was collected at days 5 and 10 to evaluate renal function. In control animals, no significant changes in any parameters were observed. In the partially obstructed fetal lambs, renal blood flow increased to 165% of baseline after 5 days; from 5 to 10 days, it decreased, but remained above baseline values through 10 days (128%). Urine production dropped significantly after 10 days (67%). Glomerular filtration rate increased slightly after 5 days (127%), but decreased after 10 (56%). Filtration fraction steadily decreased after 5 (70%) and 10 days (33%). Fractional and total sodium excretion did not change. Renal blood flow increases, filtration fraction decreases and renal function trends progressively diminish in response to partial bladder outlet obstruction over a period of 10 days in the fetal lamb.

Animals↗

PubMed1994

Pediatric ureteropelvic junction obstruction treated with retrograde endopyelotomy.

OBJECTIVES: To determine the feasibility of retrograde endopyelotomy in the management of pediatric ureteropelvic junction (UPJ) obstruction. METHODS: We treated 2 boys aged 4 and 6 years with the Acucise endopyelotomy device for symptomatic ureteropelvic junction obstruction. The Acucise device was placed over a Lunderquist guide wire with fluoroscopic guidance only and routine Double J catheters were left in situ for 6 weeks after the procedure. The morbidity of the treatment and the short-term outcome were assessed. RESULTS: There were no acute complications and short-term follow-up results were satisfactory as determined by intravenous urography and diuretic renography. CONCLUSIONS: Ureteropelvic junction obstruction in children may be treated by retrograde endopyelotomy with the Acucise device. The principal potential advantage of this procedure is reduced morbidity. Our findings suggest that further evaluation is warranted.

Catheterization↗

PubMed1994

Urodynamic and clinical follow-up of 28 children after gastrocystoplasty.

OBJECTIVES: To determine the efficacy of gastrocystoplasty in creating a large and compliant urinary reservoir. PATIENTS AND METHODS: Twenty-eight children (14 boys, 14 girls), with a median age of 9 years (range 4-17), were evaluated before and for a median of 2 years and 5 months after gastrocystoplasty. Evaluation included urodynamic and renal function studies and a survey of their post-operative complications and their sense of well-being. Renal function was assessed by ultrasound and serum creatinine, and electrolytes were measured. RESULTS: After gastrocystoplasty bladder size increased, compliance improved, hydronephrosis decreased or was stable, and renal function remained stable. There were minimal complications and the children's subjective impression of their well-being was markedly improved. CONCLUSION: Gastrocystoplasty, using our surgical technique, is a reliable method of creating a large and compliant urinary reservoir. Advantages include the absence of clinical urinary tract infections, the absence of mucus and the preservation of renal function. Complications, such as haematuria, dysuria and hypochloraemic alkalosis, might be avoided by excluding the antrum from the gastrocystoplasty, maintaining the child on a normal salt-containing diet, employing catheterization or buffering the urine in children with normal urethral sensation.

Adolescent↗

PubMed1993

Therapeutic laparoscopy for intra-abdominal testes.

Fourteen laparoscopic surgical procedures were performed in 10 children with 11 intra-abdominal testes. In addition to localizing the testes, laparoscopy aided in the surgical approach. In 8 patients, the first phase of a two-stage Fowler-Stephens orchiopexy was performed. Five children underwent an open surgical procedure three months later and have a viable testis in the scrotum after at least nine months of follow-up. In 5 patients (6 testicles), laparoscopy was used to dissect the testis. Three patients underwent the second phase of the two-stage Fowler-Stephens procedure laparoscopically. In all 3 patients, the testicle could be easily mobilized into the scrotum. Two other testicles were mobilized by dissecting the spermatic vessels up to the renal hilum laparoscopically; this allowed the intra-abdominal testes to come into the scrotum without dividing the spermatic vessels. In one teenager with a small intra-abdominal testis and a normal contralateral testis, laparoscopic orchiectomy was performed. We believe laparoscopy has a role both diagnostically and surgically in the treatment of intra-abdominal testes.

Adolescent↗

PubMed1993

Effects of endothelium-derived nitric oxide on renal hemodynamics and function in the sheep fetus.

We investigated the effects of the endothelium-derived nitric oxide system on renal hemodynamics and function during the 3rd trimester in a chronically catheterized fetal sheep preparation. Acetylcholine caused a significant decrease in renal vascular resistance (60% of the baseline value) as compared with aortic constriction (142% of the baseline value). The effects of acetylcholine could be blocked by prior administration of N omega-nitro-L-arginine (renal vascular resistance = 102% of baseline). Sodium nitroprusside also caused a significant drop in renal vascular resistance (63% of baseline), but this could not be blocked by N omega-nitro-L-arginine (77% of baseline). Infusion of N omega-nitro-L-arginine with blood pressure maintained at a constant level resulted in a significant increase in renal vascular resistance (148% of the baseline value) as compared with saline alone (94% of baseline). Glomerular filtration rate increased after saline infusion (156% of the baseline value), but this increase was blocked by N omega-nitro-L-arginine (87% of baseline). Sodium excretion also increased (340%), and this increase was blunted by N omega-nitro-L-arginine (235%). We conclude that basal production of endothelium-derived nitric oxide results in ongoing renal vasodilation in 3rd-trimester fetal sheep, maintaining baseline renal blood flow. The endothelium-derived nitric oxide system can also be stimulated to an increased level of activity, and its blockade partially prevents the homeostatic response of the fetus to volume and salt overload.

Animals↗