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PYLORIC STENOSIS

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DEFINITION

Infantile hypertrophic pyloric stenosis results from hypertrophy or enlargement of the pylorus muscle, which causes obstruction of the stomach outlet. Pyloric stenosis is one of the most common causes of gastrointestinal obstruction among infants. The defect rarely occurs in the neonate but is usually identified later in infancy. Thus, pyloric stenosis is not frequently diagnosed during the delivery admission.

DEMOGRAPHIC AND REPRODUCTIVE FACTORS

 

One of the strongest risk factors for pyloric stenosis is sex. Pyloric stenosis is more common among males than females in a variety of racial/ethnic groups, with a reported male-to-female sex ratio of 3-6.5:1 (Cooper et al., 2002a; Hedback et al., 2001; Lary and Paulozzi, 2001; Haahr and Nielsen, 2000; Gomez-Alcala, 1999; Schechter et al., 1997; Applegate and Druschel, 1995; Carneiro, 1991; Mason, 1991; Tam and Chan, 1991; Lemessa, 1990; Sharma et al., 1990; Habbick and To, 1989, Rasmussen et al., 1989; Jedd et al., 1988a; Lammer and Edmonds, 1987; Lowry et al., 1986; Webb et al., 1983; Walpole, 1981; Adelstein and Fedrick, 1976; Shim et al., 1970).

Pyloric stenosis rates vary with race/ethnicity, being much higher for whites, intermediate for Hispanics, and lower for blacks and Asians (Cooper et al., 2002a; Shaw et al., 2002; Schechter et al., 1997; Applegate and Druschel, 1995; Mitchell and Risch, 1993; Hitchcock et al., 1987; Lammer and Edmonds, 1987; Spicer, 1982; Lalouel et al., 1977; Shim et al., 1970). One investigation reported pyloric stenosis rates to be significantly lower in native Americans than in the general population (Lowry et al., 1986).

Pyloric stenosis has demonstrated a variety of secular trends. A number of studies have reported rates for the defect to increase over time (Sule et al., 2001; O'Donoghue et al., 1993; Mason, 1991; Tam and Chan, 1991; Jedd et al., 1988a; Grant and McAleer, 1984; Knox et al., 1983; Walsworth-Bell, 1983; Webb et al., 1983; Kerr, 1980). It has been suggested that part of this increase may be explained by the introduction or increased use of radiography to diagnose pyloric stenosis. "Mild" cases not identified may that have resolved without treatment before radiography use may be identified and treated once radiography is used for diagnosis. Other investigations have noted a decline in pyloric stenosis rates (Hedback et al., 2001; Haahr and Nielsen, 2000; Nielsen et al., 2000; Applegate and Druschel, 1995; Habbick and To, 1989; Dodge, 1975) while still others have reported no secular change (Rasmussen et al., 1989; Hitchcock et al., 1987; Lammer and Edmonds, 1987; Walpole, 1981; Adelstein and Fedrick, 1976).

Several studies have reported seasonal variation in pyloric stenosis rates, although the results were inconsistent (Schechter et al., 1997; Adelstein and Fedrick, 1976; Dodge, 1975), and others failed to identify any association with seasonality (Sule et al., 2001; Lemessa, 1990; Habbick and To, 1989; Rasmussen et al., 1989; Webb et al., 1983).

Investigations of the relationship between geographic location and pyloric stenosis identified decreased risk of the defect in urban areas (Applegate and Druschel, 1995; Adelstein and Fedrick, 1976). However, one study that found the pyloric stenosis rate to be lower in New York City than in the rest of New York state suggested that the difference may be due to under reporting in New York City and a higher proportion of non-whites in that city than in the rest of the state (Applegate and Druschel, 1995). An investigation reported the pyloric stenosis rate to be higher in southern Sweden than in northern Sweden (Hedback et al., 2001).

Pyloric stenosis risk has been reported by various investigations to decline with increasing maternal age (Schechter et al., 1997; Applegate and Druschel, 1995; Baird et al., 1991; Adelstein and Fedrick, 1976), although other studies found no relationship between maternal age and the defect (Rasmussen et al., 1989; Dodge, 1975; Czeizel, 1972). No association between pyloric stenosis and paternal age has been identified (McIntosh et al., 1995). Pyloric stenosis is more common at lower parity, particularly among firstborns (Schechter et al., 1997; Applegate and Druschel, 1995; Lemessa, 1990; Rasmussen et al., 1989; Jedd et al., 1988b; Dodge, 1975; Shim et al., 1970).

Several investigations have noted pyloric stenosis to be associated with increased birth weight (Applegate and Druschel, 1995; Mili et al., 1991; Lammer and Edmonds, 1987; Czeizel, 1972; Shim et al., 1970). A potential explanation for this observation is confounding by sex and/or race/ethnicity as white males tend to weigh more at delivery. However, one study found increased pyloric stenosis risk with increased birth weight among Japanese (Shim et al., 1970). Another potential explanation is that higher mortality occurs among infants with lower birth weight, so fewer of these infants survive long enough to be diagnosed with pyloric stenosis. Moreover, other literature has found pyloric stenosis to be more common among infants with low birth weight (Haahr and Nielsen, 2000; Hitchcock et al., 1987) or no relationship between the defect and birth weight (Waller et al., 2001; Schechter et al., 1997; O'Donoghue et al., 1993; Webb et al., 1983; Adelstein and Fedrick, 1976).

The results of analyses that examined gestational age and pyloric stenosis have been mixed (Rasmussen et al., 2001; Lemessa, 1990; Hitchcock et al., 1987; Adelstein and Fedrick, 1976), as have analyses of plurality and the defect (Schechter et al., 1997; Applegate and Druschel, 1995; Adelstein and Fedrick, 1976; Carter and Evans, 1969). Pyloric stenosis has not been associated with intrauterine growth retardation (Khoury et al., 1988).

Pyloric stenosis is strongly associated with a positive family history of the same defect (Haahr and Nielsen, 2000; Mason, 1991; Hitchcock et al., 1987). A genetic component for pyloric stenosis has been suggested, but its nature is unclear (Mitchell and Risch, 1993).

FACTORS IN LIFESTYLE OR ENVIRONMENT

 

In 1999, researchers examined a cluster of cases of pyloric stenosis among infants who had been given erythromycin due to exposure to pertussis and found increased risk of the defect with the antibiotic (Honein et al., 1999). Other investigations have reported increased rates of pyloric stenosis among infants who have been given erythromycin, particularly within the first two weeks after delivery (Cooper et al., 2002a; Mahon et al., 2001). However, several groups of researchers found no association between pyloric stenosis and maternal erythromycin use during pregnancy (Cooper et al., 2002b; Louik et al., 2002). One later investigation reported an increased risk of pyloric stenosis with maternal use of nonerythromycin macrolides during pregnancy (Cooper et al., 2002b).

It has also recently been hypothesized that Helicobacter pylori, a bacterium found in the human stomach, may cause some cases of pyloric stenosis in infants (Paulozzi, 2000). Pyloric stenosis has been variously associated with breastfeeding (Jedd et al., 1988b; Webb et al., 1983; Dodge, 1975) and bottlefeeding (Habbick et al., 1989).

Pyloric stenosis risk has been reported to be inversely related to maternal education (Applegate and Druschel, 1995). In contrast, the defect has also been associated with higher socioeconomic status (SES) (Lemessa, 1990; Adelstein and Fedrick, 1976; Dodge, 1975).

One investigation identified no significant association between maternal nursing occupation and pyloric stenosis (Matte et al., 1993). Another study reported an increased risk of pyloric stenosis with paternal occupation of plywood mill workers (Olshan et al., 1991); however, occupation was obtained from birth certificates.

Maternal hyperthyroidism, hypothyroidism, diabetes, and obesity do not appear to increase risk of pyloric stenosis (Aberg et al., 2001; Moore et al., 2000; Becerra et al., 1990; Khoury et al., 1989).

Several studies had found increased risk of pyloric stenosis with maternal use of Bendectin, an antinausea medication, during pregnancy (Aselton et al., 1984; Eskenazi and Bracken, 1982), although other studies failed to confirm this association (Jedd et al., 1988b; Mitchell and Risch, 1983). Pyloric stenosis has also been associated with maternal use of thalidomide, hydantoins, and trimethadione (Hoyme, 1993; Schafer and Kramer, 1987). Investigations have reported no association between maternal use of the antibiotic oxytetracycline, ampicillin, cephalosporin antibiotics, or the benzodiazepines nitrazepam, medazepam, tofisopam, alprazolum, and clonazepam during pregnancy and pyloric stenosis (Eros et al., 2002; Czeizel et al., 2001a; Czeizel et al., 2001b; Czeizel and Rockenbauer, 2000); however, maternal use of nalidixic acid to treat bacterial infection may increase risk of pyloric stenosis (Czeizel et al., 2001c).

One investigation found a lower rate of pyloric stenosis among infants whose mothers used multivitamins (Czeizel, 1993). A subsequent investigation reported a similar result, although the reduction in pyloric stenosis risk with maternal multivitamin use was not significant (Werler et al., 1999). No association between maternal folic acid use and pyloric stenosis has been reported (Czeizel et al., 1996). Furthermore, a study that examined co-trimoxazole, a combination of trimethoprim and sulfamethoxazole that is a folic acid antagonist, failed to find any association between the medication and pyloric stenosis (Czeizel et al, 1990).

PREVALENCE

The reported prevalence for pyloric stenosis has shown variation between studies, ranging between 10.6 and 43.3 per 10,000 births (Table 1). Differences in prevalence may be due to differences in case inclusion criteria.

Table 1. Prevalence per 10,000 births of pyloric stenosis

Reference Location Time period Rate
Sekhobo and Druschel, 2002 New York, USA 1996 17.8
Hedback et al., 2001 Sweden 1987-1996 19.2
Sule et al., 2001 Scotland 1980-1996 36
Nielsen et al., 2000 Denmark 1977-1997 23.9
Schechter et al, 1997 California, USA 1983-1988 19.1
Appelgate and Druschel, 1995 New York, USA 1983-1987 18
O'Donoghue et al, 1993 Ireland 1981-1990 43.3
Rasmussen et al., 1989 Denmark 1950-1984 31.0
Lowry et al., 1986 Canada 1966-1981 30.6
Grant and McAleer, 1984 Northern Ireland 1971-1983 31.4
Knox et al., 1983 Scotland 1974-1980 26.9
Czeizel and Vitez, 1981 Hungary 1970-1977 15.1
Shim et al., 1970 Hawaii, USA 1942-1966 10.6

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  • Walsworth-Bell JP. Infantile hypertrophic pyloric stenosis in Greater Manchester. J Epidemiol Community Health 1983;37:149-152.
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Please Note: The primary purpose of this report is to provide background necessary for conducting cluster investigations. It summarizes literature about risk factors associated with this defect. The strengths and limitations of each reference were not critically examined prior to inclusion in this report. Consumers and professionals using this information are advised to consult the references given for more in-depth information. 

This report is for information purposes only and is not intended to diagnose, cure, mitigate, treat, or prevent disease or other conditions and is not intended to provide a determination or assessment of the state of health. Individuals affected by this condition should consult their physician and when appropriate, seek genetic counseling.

 

 
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Last updated February 10, 2012