Sonography of hypertrophic pyloric stenosis: frequency and cause of nonuniform echogenicity of the thickened pyloric muscle.

In hypertrophic pyloric stenosis, the muscle is typically described as hypoechoic on sonography. However, we have frequently noted a nonuniform pattern; the pyloric muscle seen in the transverse plane is more echogenic in the near and far fields and less echogenic on the sides. The muscle also appears almost as echogenic as the liver on midline longitudinal sonograms. To establish the frequency of these findings, we reviewed the sonograms of 71 infants with hypertrophic pyloric stenosis. The muscle was imaged directly during surgery in three patients. In an in vitro experiment, muscle arranged to stimulate the pyloric ring was scanned in a water bath. Then, using two sections of muscle, we compared the echogenicity when scanning in a plane perpendicular to the long axis of the muscle fibers with that seen with the beam parallel to the long axis of the muscle fibers. In the transverse plane, nonuniform echogenicity of the pyloric muscle was seen in 59 (98%) of 60 patients. In the midline longitudinal plane, the muscle was equal to or slightly less echogenic than the liver in all patients. Both the in vivo and in vitro studies show that the echogenicity varies with the relationship of the ultrasound beam to the orientation of the circular muscle fibers; this phenomenon is known as the anisotropic effect. Our results show that nonuniform echogenicity of the hypertrophied pyloric muscle is a characteristic sonographic finding caused by the anisotropic effect, which is related to the orientation of the ultrasound beam with respect to the circular fibers of the pyloric muscle.

Necrotizing enterocolitis in a neonatal piglet model.

The aim of this study was to develop an animal model for necrotizing enterocolitis (NEC). Twenty-five neonatal Hanford minipigs had carotid artery and external jugular vein catheters and rectal Clinical Tonomitors placed under anesthesia. Experimental animals were subjected to a hypoxic insult (50% reduction in baseline PaO2 for 30 minutes) and hypothermic stress (core temperature reduced to 35 degrees C for 30 minutes). Regular oral diet was resumed and the survivors were euthanized 3 to 4 days later. All animals underwent necropsy with gross and histopathological evaluation of the entire bowel. Of 22 experimental animals, 14 survived (64%) and 8 (36%) died of pulmonary hemorrhage. Of the 14 survivors, 8 (57%) had gross and microscopic evidence of NEC. Six of the total 25 animals (24%) sustained rectal perforations from the tonometer. Of 3 control animals, one died of pulmonary hemorrhage and the two survivors had normal intestine. This model successfully produced gross and histological evidence of NEC. The tonometer shows promise as a predictor of NEC provided technical modifications can reduce the complication rate.

The effects of enteral stimulation on gallbladder bile during total parenteral nutrition in the neonatal piglet.

The neonatal piglet is a satisfactory model for the human neonate requiring total parenteral nutrition (TPN). Bile status and subsequent liver and gallbladder dysfunction have long been documented as serious complications of long-term TPN. The purpose of this study was to determine whether small amounts of enteral formula during TPN will maintain normal bile appearance and composition. Thirty-one Hanford miniswine, 3 to 6 days old underwent surgery for the placement of central venous catheters. Two days postoperatively, the animals were separated into three groups, according to dietary regimens. Group 1 (n = 10), the control group, received pig formula (SPF-lac) orally (200 cal/kg/d); group 2 (n = 11), was maintained on TPN (180 cal/kg/d) with an enteral supplement of SPF-lac (20 cal/kg/d); group 3 (n = 10), was maintained on TPN only (200 cal/kg/d). The TPN formula consisted of 35 g/kg/d of glucose, 10 g/kg/d of protein, and 3 g/kg/d of lipid. The animals were maintained on these diets for 6 weeks. At necropsy, gallbladder with bile was weighed and bile volume and appearance was recorded. Chemical analyses was performed on 26 bile samples. Gallbladder weight was significantly decreased in groups 2 and 3 compared with group 1 (P less than .0003, P less than .033, respectively, using Students t test with Bonferoni adjustment). Volume was significantly decreased only in group 2 (P less than .003). Group differentiation in relation to bile appearance was determined by the presence or absence of either bile sludge or crystals.(ABSTRACT TRUNCATED AT 250 WORDS)

Atretic esophagus: transgastric balloon-assisted hydrostatic dilation.

Esophageal atresia may be associated with a long interval or gap between the upper and lower pouches. Despite a variety of procedures to elongate the esophagus, surgeons have been unable to achieve esophageal continuity in many patients. Three infants with esophageal atresia and long gaps recently underwent hydrostatic dilation of the distal esophageal pouch followed by primary anastomosis. The technique entailed passing a balloon-tipped catheter through a gastrostomy site to the distal esophageal pouch. The balloon was inflated to a diameter sufficient to occlude the distal esophagus. Dilute contrast material was then infused under fluoroscopic visualization to a maximal pressure of 145 cm H2O. Dilations were performed daily over a 2-week period, followed by surgery. Primary anastomosis was accomplished in all patients. The promising results in these patients should stimulate other investigators to assess this technique in infants with this challenging surgical problem.

The normal diameter of the fetal aorta and pulmonary artery: echocardiographic evaluation in utero.

Measurements of the fetal aorta and pulmonary artery can aid in the detection and diagnosis of congenital heart defects. In a prospective study of 403 normal fetuses whose gestational ages were between 14 and 42 weeks, two-dimensional (2D) real-time and M-mode echocardiography were used to measure the diameters of the aortic root and the pulmonary artery in utero. The goals were to establish norms for the diameters of these structures as a function of both gestational age and biparietal diameter, to compare measurements obtained in systole and diastole, and to compare 2D and M-mode measurements. A high correlation was found between measurements made during systole and diastole (r = .994 for aorta, r = .996 for pulmonary artery) and between 2D and M-mode measurements for each vessel (r = .992 for aorta, r = .973 for pulmonary artery). The differences between systolic and diastolic measurements and between M-mode and 2D measurements were small (2.2-4.6%) for both the aorta and the pulmonary artery. The norms established here provide an objective standard for comparison when a cardiac anomaly involving a fetal aorta or pulmonary artery of abnormal size is suspected. The results indicate that a sonographic facility need not have M-mode equipment to obtain technically adequate measurements.