Porcine models for pediatric minimally invasive surgical training--a template for the future.

Pediatric minimally invasive surgery is a rapidly developing field with a steep learning curve for each new procedure that is developed and integrated into practice. The European consensus is that the training across the learning curve should not be on the patients. Simulation is a widely accepted methodology to shorten the learning curve. Training on animal models is an advanced form of simulation. This helps to reduce morbidity and the costs of patient care. This article describes our 3 years of experience in the development of animal models for training in pediatric minimally invasive surgery.

Evaluation and management of the abnormal gonad.

Diagnostic evaluation of patients with an abnormal gonad is complex because of multifactoral etio-pathogenesis and rarity of the conditions. In the text to follow, we have briefly discussed the embryology and attempted to classify abnormal gonadal disorders. The aims of evaluating such a child are to: (1) establish genetic sex; (2) determine the hormonal milieu; (3) evaluate the anatomy of internal and external genitalia and gonads; and (4) in older children, assess the phenotypic and psychological sex. In newborn children with ambiguous genitalia, the focus is now on accurate gender assignment. A team approach is needed and decisions are based on likely prognosis for behavior and gender orientation. The recent advances in cytogenetics have proven to be helpful in early and accurate diagnosis. In patients with an abnormal gonad, four conditions can present with sexual ambiguity at birth: female pseudohermaphroditism (or "virilized female"), true hermaphroditism, male pseudohermaphroditism (or "undervirilized male") and mixed gonadal dysgenesis. The role of clinical history and examination is emphasized in differential diagnosis and management. Timing of surgery for each of the conditions is discussed.

Gubernacular cell division in different rodent models of cryptorchidism supports indirect androgenic action via the genitofemoral nerve.

PURPOSE: The role of the "gubernaculum" in testicular descent remains controversial. Androgens are proposed to act indirectly by the genitofemoral nerve (GFN) releasing calcitonin gene-related peptide. The authors studied the effects of sensory nerve ablation and androgen blockade on mitosis in the gubernacular tip to determine whether androgens act directly or indirectly. METHODS: Five rat models were examined for bromodeoxyuridine (BUdR)-labeling: (i) Sprague-Dawley (SD) rats (controls), (ii) prenatal flutamide-treated rats (75 mg/kg to dams on D16-19 gestation), (iii) neonatal capsaicin-treated rats (50 mg/kg, subcutaneous on day 0), (iv) congenitally cryptorchid transcrotal (TS) rats, and (v) capsaicin-treated TS rats (50 mg/kg, subcutaneous on day 0). Newborn rats were collected at days 0, 2, 4, 6, 8, and 10 (age, n = 5/model, n = 30) and were injected intraperitoneally with 1 mg/kg BUdR, 2 hours before killing. Histological sections of gubernaculum were examined immunohistochemically for BUdR labeling. RESULTS: In SD (control) rats, DNA synthesis in the gubernacular tip was high at birth, reached a peak at day 2, and then decreased progressively until day 10. A similar pattern was observed in TS rats. However, quantitatively, the levels were significantly higher. In flutamide-treated rats, DNA synthesis was suppressed until day 6, similar suppression was observed in capsaicin-treated SD, and TS rats until day 4. CONCLUSIONS: Flutamide, a competitive androgen receptor blocker, reduces gubernacular mitosis to basal levels until day 6, highlighting the importance of androgen receptor. Excess DNA accumulation in TS rats is consistent with the known excess of GFN fibers and calcitonin gene-related peptide in this mutant. Capsaicin-inhibited mitosis in both day 2 SD and TS rats suggests that the GFN mediates androgen action on early postnatal gubernacular DNA synthesis and growth.

Radionuclear transit to assess sites of delay in large bowel transit in children with chronic idiopathic constipation.

PURPOSE: Chronic idiopathic constipation (CIC) with soiling in children may result from slow colonic transit (SCT) or anorectal dysfunction and/or psychological problems known as functional fecal retention (FFR). Evidence is accumulating that SCT and FFR need different treatments, but they are poorly distinguished by solid marker studies. The authors used radionuclear transit scintigraphy to categorize children with CIC as having either FFR or SCT. METHODS: Children (N = 101) with CIC (and soiling) who were referred for further investigation after failure of standard treatments (diet, laxatives) received radiolabeled colloid orally, and scintillation images were collected at 0 to 2, 6, 24, 30 and 48 hours (total radiation dosage = 2 standard x-rays). Radioactivity in 6 regions (precolonic, ascending, transverse, descending, rectosigmoid, and evacuated feces) was measured, and the median position (geometric center) of radioactivity at each time was determined. RESULTS: In children, meals normally reach the cecum at 6 hours and are evacuated in 30 to 58 hours. Fifty patients had retention of radioactivity in the proximal colon at 48 hours, indicating SCT. Analysis of the images and the geometric center showed that passage through the ascending colon and transverse colon was delayed in SCT. In 24 patients, radioactivity was passed by 30 hours, indicating normal transit or possible FFR. Twenty-two patients had retention in the rectum, indicating definite FFR. Five studies were borderline. CONCLUSIONS: Radionuclear transit scintigraphy is useful for categorizing patients with CIC as having either FFR or SCT, allowing for different treatments. Radionuclear transit scintigraphy provides more detail and greater sensitivity than solid marker studies in diagnosing CIC. Radionuclear transit scintigraphy showed that half of our patients had SCT.