Use of spiral computerized tomography in lieu of angiography for preoperative assessment of living renal donors.

PURPOSE: We evaluate whether spiral computerized tomography (CT) can be used in lieu of renal angiography for preoperative assessment of living renal donors, with special attention to multiplicity of renal vasculature. MATERIALS AND METHODS: A total of 47 living renal donor candidates were evaluated with spiral CT and all but 2 underwent donor nephrectomy. Patients were divided into early and late groups because there was a learning curve with spiral CT. In the early group 18 donors underwent renal angiography as well as spiral CT and 10 underwent nephrectomy after spiral CT only. In the late group 5 had dual radiographic evaluation for ambiguities in spiral CT interpretation and 12 underwent nephrectomy after spiral CT only. Spiral CT was performed and interpreted blind to angiographic results, and vice versa. RESULTS: Spiral CT identified 50 of 52 renal arteries (96%) found at surgery overall and 23 of 25 (92%) found at surgery after spiral CT only. Two accessory arteries were missed in the 10 early group donors evaluated with spiral CT only, yielding an early negative predictive value of 80%. Renal angiography identified another accessory artery missed by spiral CT in the early group. All 3 missed vessels were identified retrospectively. No arteries found at surgery were missed in the late group (negative predictive value 100%), although there were 2 false-positive results detected by spiral CT relative to renal angiography in 1 candidate renal unit. Overall accuracy to predict early renal artery division relative to surgical findings was 93% for spiral CT and 91% for renal angiography. However, early renal artery division was clinically significant for only 1 of 11 vessels found at surgery. Spiral CT demonstrated 4 anomalous venous returns and renal angiography identified none. However, spiral CT missed 2 accessory veins and identified only 1 of 2 fibromuscular dysplasia cases. Total cost for spiral CT and renal angiography was $886 and $2,905, respectively. CONCLUSIONS: Spiral CT is a reasonably good alternative to renal angiography for living renal donor assessment but there is a profound learning curve for performance and interpretation. Renal angiography is still the gold standard with respect to the identification of arterial multiplicity and fibromuscular dysplasia, and it should be used adjunctively in cases with spiral CT ambiguity. Neither spiral CT nor renal angiography is ideal for the assessment of early renal artery division which is seldom an issue. The benefits of spiral CT over renal angiography are potentially lower morbidity, improved donor convenience and reduced cost.

Economic correlates of nonmarital childbearing among adult women.

The growth of nonmarital childbearing among women who are beyond their teenage years is well documented. Very little is known, however, about the economic status of these women. Data for 1991 from the nationally representative Panel Study of Income Dynamics indicate that the socioeconomic status of women who have had a nonmarital birth as an adult is similar to that of women who had a birth as an adolescent: They have similar median income-to-needs ratios (2.29 vs. 2.17), and similar rates of poverty (20% vs. 23%) and welfare receipt (22% vs. 19%). Women who have had both teenage and postteenage nonmarital births fare particularly poorly: Their median family income is $11,280; nearly half receive welfare; and 55% are officially poor. However, women who first gave birth as adolescents but have not had subsequent nonmarital births do reasonably well: Fewer than 10% receive welfare, and their median income-to-needs ratio is 2.6.

Nonmarital childbearing in the 1980s: assessing the importance of women 25 and older.

Nonmarital births to women in their late 20s and 30s have attracted increasing attention in recent years. Marital and birth history data from the Panel Study of Income Dynamics confirm that births to unmarried women aged 25 and older accounted for a larger proportion of all nonmarital births in the 1980s than in the 1970s (36% vs. 22%). Most of these births were to women who had been previously married or who had other children: Births to never-married, first-time mothers aged 25 and older accounted for only 9% of all nonmarital births to older women in the 1980s. The majority of nonmarital births to older women in the 1980s-58%-involved women who began having children as teenagers.

PIP: This analysis of marital and birth history data from the 1985-91 US Panel Study of Income Dynamics focuses on nonmarital childbearing. The total sample included 733 nonmarital births to 595 women from 1970 to 1979 and 933 nonmarital births to 741 women from 1980 to 1989. The sample for this study is confined to women aged 25 years and older or 117 births to 96 women in the 1970s and 280 births to 217 women in the 1980s. The analysis is based on births and not women. Findings indicate a shift to a greater proportion of nonmarital births to women aged 25 years and older, from 22% in the 1970s to 36% in the 1980s. However, only 15% of births were to women who were childless during their 20s. 58% of nonmarital births were to women who began childbearing as teenagers, and 46% of nonmarital births were to never married women who began childbearing as adolescents. Over 40% of births among women aged 25 years and older were to women who had been previously married. 33% of births were to women who had a first birth as teenagers, and almost 20% were to women aged under 18 years with a first birth. 19% of nonmarital births were to women with a previous marital birth, which was a considerable decline from the 1970s. 7% of nonmarital births were to women who had a previous marital birth and a previous nonmarital birth. Only 25% of births to women aged 25 years and older were to women with first births. 16% were to never married women with first births, which was a considerable decline from the 1970s. Racial differences occurred in nonmarital births between the 1970s and the 1980s. There is concern about the increased number of never married women older than 25 years with nonmarital births, because the increase amounted to a rise of 60% between decades. The authors point out that the lack of a formal marriage did not rule out the absence of contact with a father.

The effect of divorce on intergenerational transfers: new evidence.

This paper draws on new data on intergenerational transfers of time and money that were collected in the Panel Study of Income Dynamics. We use these data to examine the effects of divorce on these transfers. We find that the timing of divorce is critical. Fathers and mothers involved in late divorces have similar levels of transfers with their adult children, while divorce during a child's childhood years increases transfers with mothers and sharply lowers them with fathers. Somewhat surprisingly, we find no evidence that divorced fathers who paid child support are more likely to be involved in intergenerational transfers than those who did not pay child support.

Reevaluating the costs of teenage childbearing.

Teenage childbearing in the United States has long been regarded as an important social problem with substantial costs to teen mothers and their children. Recently, however, several researchers have argued that the apparent negative effects of teenage childbearing primarily reflect unmeasured family background rather than the true consequences of a teen birth. To distinguish the effect of teen childbearing from that of family background, we use data from the Panel Study of Income Dynamics and compare teen mothers with their sisters. We find that accounting for unobserved family background reduces, but does not eliminate, the estimated consequences of early childbearing. Statistically significant and quantitatively important effects of teen parenthood remain for high school graduation, family size, and economic well-being.

Effect of flexion angle on the pressure-volume of the human knee.

The objective of this study was to determine pressure-volume relationships in the human knee. Eight normal knees in eight patients undergoing elective arthroscopic surgery were studied to develop pressure-volume curves at 0 degrees, 15 degrees, 30 degrees, 60 degrees, and 80 degrees of flexion, and measure capsular volume at 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 80 degrees of flexion. The results showed that capsular volume decreases with flexion, whereas capsular stiffness increases. This suggests that during arthroscopy, flexion with obstructed outflow may cause significant intraarticular pressure and potential rupture of synovial membranes. Our results support the concept of flow rates with low distension pressures for maximum safety.

Welfare benefits, economic opportunities, and out-of-wedlock births among black teenage girls.

This article presents a model of teenage out-of-wedlock births that incorporates the effects of both welfare and nonwelfare economic opportunities. We construct measures of the likely "medium-run" income available to a teenage girl in the event of an out-of-wedlock birth and in the absence of a birth and then estimate a logit model to determine their importance in influencing fertility behavior. The model is estimated with data from the Panel Study of Income Dynamics on nearly 900 black teenagers. We find weak and statistically insignificant positive effects of Aid to Families With Dependent Children (AFDC) benefit levels and stronger and significant negative effects of economic opportunities on the probability of AFDC-related out-of-wedlock teen births.

Teenage welfare receipt and subsequent dependence among black adolescent mothers.

Black teenage mothers who receive benefits through Aid to Families with Dependent Children (AFDC) around the time they give birth are more likely to be receiving AFDC at age 26 than are other black teenage mothers or women who do not have a teenage birth, even after adjustments are made for differences in parental background and the economic accomplishments of siblings. Moreover, they are also more likely to have a lower earned family income and a lower total family income (when transfer income such as AFDC is taken into account). The results of this analysis suggest that AFDC receipt around the time of a nonmarital teenage birth itself may be an independent cause of future economic problems for these young mothers, although they do not elucidate the causal mechanism by which such an association might operate.

What are the economic consequences of divorce?

Our analysis suggests that Weitzman's finding concerning the precipitous decline in the economic status of women following divorce is likely to be incorrect. Her findings not only imply improbably large changes in income but are also inconsistent with the information she reports on changes in income and in income per capita. Corrected estimates suggest a decline in economic status of about one-third, rather than the widely cited 73 percent figure. It remains the case that the economic status of men and women diverge substantially in the years after divorce. That difference, however, is not nearly as dramatic as suggested by Weitzman's findings.

Multinomial and conditional logit discrete-choice models in demography.

Although discrete-choice statistical techniques have been used with increasing regularity in demographic analyses, McFadden's conditional logit model is less well known and seldom used. Conditional logit models are appropriate when the choice among alternatives is modeled as a function of the characteristics of the alternatives, rather than (or in addition to) the characteristics of the individual making the choice. We argue that this feature of conditional logit makes it more appropriate for estimating behavioral models. In this article, the conditional logit model is presented and compared with the more familiar multinomial logit model. The difference between the two techniques is illustrated with an analysis of the choice of marital and welfare status by divorced or separated women.

Welfare dependence within and across generations.

A central question in the debate about the effects of welfare programs is whether their intended positive results--providing needed resources to recipients and their children--outweigh any unintended negative results--for example, the breaking up of families, reduction in work effort, or the fostering of a welfare "culture" that is passed on from parent to child. Recent research shows that although work effort is affected adversely by the generosity of welfare programs, effects on family structure appear quite weak, most welfare experiences are relatively short, and the majority of women who grew up in homes heavily dependent on welfare do not rely on those programs when they are young adults.

A reconsideration of the economic consequences of marital dissolution.

A close look at the income flows in the years following a divorce or separation reveals marked differences in the distribution of effects. The economic consequences of divorce are especially adverse for women. In most cases, children remain with the mother, who usually has considerably lower potential labor market earnings than her former husband, partly because her responsibilities for the children are likely to reduce her labor supply and may have limited her past human capital investments. Alimony and child support are the principal mechanisms for transfers from the ex-husband to the ex-wife, but payments are rarely frequent or sizeable enough to make up for an appreciable amount of the labor income lost through the departure of the ex-husband. Human capital investments on the part of the mother have a modest effect on her economic situation in the years following the divorce. Most men who divorce or separate are immediately better off because they retain most of their labor incomes, typically do not pay large amounts of alimony and child support to their ex-wives, and no longer have to provide for the level of needs associated with their former families. Much more important than growth in the ex-wife's own labor income is the role of a new husband's labor income upon her remarriage. More than half of the white women remarry within five years following a divorce or separation; the comparable fraction for black women is less than half. An interesting question is whether the currently unmarried would enjoy the same kind of economic benefits, were they to remarry, as women who have remarried. Estimates from a model of the new husband's labor income, adjusted for selection bias inherent in the process of remarriage, indicate that the currently unmarried would probably not gain equal benefits if they were to remarry. The expected labor income of potential husbands of black women averages only about $5000--a modest amount when compared with the alternatives available to these women.