Obstetric sonography. Who to scan, when to scan, and by whom.

Most patients in the United States have an indication for and receive sonography during pregnancy. The issue of routine sonography for low-risk women continues to be contentious even though the randomized trials have not been able to demonstrate a clear benefit. Clinics that routinely offer sonography for all pregnancies usually schedule such a procedure at 16 to 20 weeks of gestation. Although great progress is being made in the first-trimester diagnoses of congenital anomalies, most targeted studies are performed at 18 to 20 weeks of gestation. Although many private obstetricians perform in-office sonography, the highest rates of detection of congenital anomalies are seen in tertiary care settings such as a university medical center. In difficult or otherwise high-risk cases, a consulting perinatologist is commonly the physician most likely to integrate the ultrasound findings with a rational management plan for the remainder of the pregnancy and for delivery.

Hereditary persistence of fetal hemoglobin presenting as fetal-maternal hemorrhage.

This report describes a case of hereditary persistence of fetal hemoglobin (HPFH) presenting initially as a marginal placental abruption in a primiparous woman at 27 weeks gestation. Persistent but erratic elevation of percent hemoglobin F positive cells, as determined by a modified Kleihauer-Betke method, complicated the remainder of her pregnancy. The clinical impression of placental abruption with possible extension could not be documented by ultrasound or examination of the placenta at delivery. Hemoglobin electrophoresis followed by quantitative fetal hemoglobin first suggested the diagnosis of HPFH, which was confirmed seven months postpartum. Furthermore, the magnitude of percent positive F-cells could be profoundly altered by subtle changes in pH of the acid elution reagent. This case demonstrates that positive acid elution tests for maternal-fetal transfusion may be caused by elevated maternal hemoglobin F. Erratic results, elevated quantitative hemoglobin-F and sensitivity to reagent pH should alert the pathologist to this diagnosis and alter clinical management.

The adolescent varicocele. A histopathologic study of 13 testicular biopsies.

Testicular varicocele, the most common cause of male infertility, frequently presents in early adolescence. To determine whether testicular damage occurs early in the natural history of varicocele, testicular biopsy specimens from 13 patients, 13 to 18 years of age (mean age, 15.5 years), were studied. The biopsies were compared with testicular tissue from six normal control subjects 15 to 28 years of age (mean age, 23.2 years). Nine of the patients with varicoceles (69.2%) demonstrated some degree of tubular sclerosis. Ultrastructural study demonstrated that the tubular sclerosis was due to collagen deposition by fibromyocytes in the peritubular sheath. Premature germ cell sloughing was present in greater than 50% of tubules examined in all but one biopsy. Six patients (46%) demonstrated small vessel sclerosis. Quantitation of the germinal epithelium revealed that the mean germ cell/Sertoli cell ratio and the percentage of germ cells present as late stage forms (secondary spermatocytes, spermatids and spermatozoa) were significantly reduced in the varicocele group. The testes of two patients exhibited severe hypospermatogenesis approaching germ cell aplasia. None of these changes were seen in the control group. The authors conclude that pathologic changes in the testes of patients with varicoceles are found at or soon after puberty. The histopathologic features include peritubular sclerosis, small vessel sclerosis, premature germ cell sloughing, and variable degrees of hypospermatogenesis.

Simulated propagation of cardiac action potentials.

We have used numerical methods for solving cable equations, combined with previously published mathematical models for the membrane properties of ventricular and Purkinje cells, to simulate the propagation of cardiac action potentials along a unidimensional strand. Two types of inhomogeneities have been simulated and the results compared with experimentally observed disturbances in cardiac action potential propagation. Changes in the membrane model for regions of the strand were introduced to simulate regions of decreased excitability. Regional changes in the intercellular coupling were also studied. The results illustrate and help to explain the disturbances in propagation which have been reported to occur at regions of decreased excitability, regions with changing action potential duration, or regions with changing intercellular coupling. The propagational disturbances seen at all of these regions are discussed in terms of the changing electrical load imposed upon the propagating impulse.