(Radiology. 2001;219:91-94.)
© RSNA, 2001
Frequency of Right Lower Quadrant Position of the Sigmoid Colon in Infants and Young Children1
David J. Fiorella, MD and
Lane F. Donnelly, MD
1 From the Department of Radiology, Duke University Medical Center, Durham, NC (D.J.F.); and the Department of Radiology, Children’s Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229-3039 (L.F.D.). Received May 16, 2000; revision requested June 19; revision received July 22; accepted July 25. Address correspondence to L.F.D. (e-mail: donnelly.lf@chmcc.org).
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ABSTRACT
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PURPOSE: To evaluate the frequency of right lower quadrant positioning of the sigmoid colon in infants and young children.
MATERIALS AND METHODS: Findings in 169 patients who underwent enema examination were retrospectively reviewed. Sigmoid colon position was categorized as in the left or right lower quadrant or midline. Patients who had an anatomic abnormality that affected colonic position (eg, malrotation or abdominal mass) or had previously undergone abdominal surgery were excluded. The frequency of right lower quadrant sigmoid position was evaluated for a relationship with patient age (analysis of variance) and sex (
2 test).
RESULTS: Patient ages were 1 day to 5 years (mean age, 13 months). The sigmoid colon was in the right lower quadrant in 74 (44%), in the left lower quadrant in 73 (43%), and in the midline in 18 (11%). The position was variable in one patient and indeterminate in three. When the sigmoid colon was within the right lower quadrant, it often extended laterally, overlying the position of the cecum and ascending colon. There were no significant correlations between right lower quadrant position and patient age (P = .262) and sex (P = .162).
CONCLUSION: In children, the sigmoid colon is often within the right lower quadrant. Knowledge of this high frequency should reduce the likelihood of misinterpreting air within a redundant right-sided sigmoid colon as air within the cecum in children suspected of having abnormalities such as intussusception.
Index terms: Children, gastrointestinal tract, 756.139 • Intestines, 756.139 • Normal variant, 756.139
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INTRODUCTION
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The accurate identification of bowel within the right lower quadrant as cecum at radiography is an important task in the radiographic evaluation of pediatric gastrointestinal diagnoses such as intussusception (1–4) and malrotation (5,6). Although there is some variation in the position of the sigmoid colon in adults, depending on the degree of redundancy, with most variations, most if not all of the sigmoid colon seen in adults is within the left lower quadrant (7). We noticed that, on radiographs from enema examinations in young children, the sigmoid colon often is positioned within the right lower quadrant. The sigmoid colon, when positioned within the right lower quadrant, could be mistaken for the cecum and ascending colon and lead to misinterpretation of findings, especially in children being examined for intussusception. A search of the literature (PUBMED [8], key words: normal variant, colon, sigmoid, right lower quadrant, position) yielded little or no published information concerning normal variations in the position of the sigmoid colon in young children. The purpose of this study was to evaluate the frequency of right lower quadrant position of the sigmoid colon in infants and young children.
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MATERIALS AND METHODS
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Radiographs from 169 enema examinations performed in the Division of Pediatric Imaging at Duke University were retrospectively evaluated for the position of the sigmoid colon. All examinations had been performed for clinical indications. One hundred thirty of the examinations were performed with positive liquid contrast agents, and 39 were performed with air alone to evaluate for possible intussusception. Although the exact spot radiographs obtained at each examination varied with the clinical indication and the individuals performing the procedure, in all examinations, frontal views demonstrating the abdomen were available. These frontal views were used to determine the position of the sigmoid colon.
Only children 5 years of age or younger were included in the study. All clinical data and radiographs from the examinations were reviewed by both authors in consensus. Patient ages and the diagnoses suggested by examination findings were recorded. Patients excluded from the study group included those with an anatomic abnormality that potentially affected colonic position, such as malrotation, abdominal mass, or a history of previous abdominal surgery. Initially, 201 patients were considered for the study. Thirty-two were excluded on the basis of either the preceding criteria or having undergone an examination for which radiographs could not be found.
The position of the sigmoid colon was categorized as being in the left lower quadrant, right lower quadrant, or midline. The sigmoid colon was categorized as being in the left lower quadrant if most or all of the loops of the sigmoid colon were to the left of the lumbar vertebral bodies. The sigmoid colon was categorized as being in the right lower quadrant if one or more complete loops of sigmoid colon were to the right of the lumbar vertebral bodies. There were no criteria for upper versus lower quadrant position. Because, in a majority of cases, most of all of the sigmoid colon was isolated to the lower quadrant, this group is referred to as right lower quadrant. However, in some cases, part of the sigmoid colon extended into the right upper quadrant. The sigmoid colon was categorized as being in the midline if it extended superiorly in a vertical orientation, overlying the midline to the level of the second lumbar vertebrae before entering the right or left side of the abdomen. If the sigmoid colon moved from one category of position (left, right, or midline) to another during the examination, it was considered to have variable position. If the position of the sigmoid colon could not be determined from the images recorded during the examination because of overlapping opacified bowel, the position was considered indeterminate. The position of the sigmoid colon was determined by means of consensus of both authors.
The frequencies for each position of the sigmoid colon were calculated, and these frequencies were evaluated for a relationship with patient age and sex. The 2 test was performed to evaluate a relationship between patient sex and sigmoid colon position, and analysis of variance was performed to evaluate a relationship between patient age and sigmoid colon position. A P value of less than .05 was considered to indicate a significant difference.
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RESULTS
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The ages of the 169 subjects ranged from 1 day to 5 years (mean age, 13 months). There were 82 boys and 87 girls. In 131 (78%) of the patients, the colon was considered normal. Diagnoses suggested by enema examination findings included Hirschsprung disease in 11, meconium ileus in one, meconium plug syndrome or small left colon syndrome in 10, postnecrotizing enterocolitis stricture in two, and intussusception in 14.
With regard to the position of the sigmoid colon, in 73 (43%) patients, the sigmoid colon was within the left lower quadrant. In 74 (44%) patients, one or more loops of the sigmoid colon were within the right lower quadrant (Fig 1). In 18 (11%) patients, the sigmoid colon was in the midline (Fig 2). The position was variable in one patient (Fig 3). In three patients, the position of the sigmoid colon was indeterminate. When the sigmoid colon was within the right lower quadrant, it often extended into the rightmost lateral portion of the abdomen and overlaid the expected position of the cecum and ascending colon (Figs 1, 3, 4).
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Figure 1. Frontal radiograph from enema examination in a 3-year-old boy shows the sigmoid colon (S) within the right lower quadrant of the abdomen; it overlies the expected position of the cecum and ascending colon.
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Figure 3a. Frontal radiographs from enema examination show change in the position of the sigmoid colon (S), with progressive colonic distention, in a 5-day-old male infant. (a) Early image shows sigmoid colon looped in the right lower quadrant of the abdomen. (b) Later image shows the sigmoid colon as extending superiorly into the right upper quadrant of the abdomen.
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Figure 3b. Frontal radiographs from enema examination show change in the position of the sigmoid colon (S), with progressive colonic distention, in a 5-day-old male infant. (a) Early image shows sigmoid colon looped in the right lower quadrant of the abdomen. (b) Later image shows the sigmoid colon as extending superiorly into the right upper quadrant of the abdomen.
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Figure 4a. Frontal radiographs from enema examination show the right lower quadrant position of the sigmoid colon (S) in children of various ages. (a) Image in a 7-day-old male infant shows the sigmoid colon in the right side of the abdomen, lateral to the cecum (C). (b) Image in a 5-year-old girl shows the sigmoid colon in the right lower quadrant. The lateral portion of the sigmoid colon has a course that could cause it to be mistaken for the ascending colon at radiography. The cecum is not yet opacified with contrast material.
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Figure 4b. Frontal radiographs from enema examination show the right lower quadrant position of the sigmoid colon (S) in children of various ages. (a) Image in a 7-day-old male infant shows the sigmoid colon in the right side of the abdomen, lateral to the cecum (C). (b) Image in a 5-year-old girl shows the sigmoid colon in the right lower quadrant. The lateral portion of the sigmoid colon has a course that could cause it to be mistaken for the ascending colon at radiography. The cecum is not yet opacified with contrast material.
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There was no significant correlation between patient age and the position of the sigmoid colon (P = .262) (Fig 4). The mean patient age was 14.4 months in children whose sigmoid colon was in the left lower quadrant; 11.1 months, in the right lower quadrant; and 17.4 months, in the midline. There was no significant correlation between patient sex and the position of the sigmoid colon (P = .162). In the 87 girls, the sigmoid colon was in the right lower quadrant in 43 (49%), in the left lower quadrant in 34 (39%), and in the midline in eight (9%). In two (2%) patients, the sigmoid colon position was indeterminate. In the 82 boys, the sigmoid colon was in the right lower quadrant in 31 (38%), in the left lower quadrant in 39 (48%), and in the midline in 10 (12%). In one (1%) patient, the position of the sigmoid colon was variable and in another (1%) was indeterminate.
The results were similar when only the 131 patients with normal radiographs were considered. In 54 (41%) patients, the sigmoid colon was within the left lower quadrant. In 63 (48%) patients, one or more loops of the sigmoid colon were within the right lower quadrant. In 11 (8%) patients, the sigmoid colon was vertically oriented. In three (2%) patients, the position of the sigmoid colon was indeterminate.
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DISCUSSION
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We have shown that the sigmoid colon is often normally positioned within the right lower quadrant in young children. Knowledge of this high frequency should reduce the likelihood of misinterpreting air within a redundant right-sided sigmoid colon as air within the cecum in children being examined for a suspected abnormality. There are a number of important childhood diseases in which identifying an air-filled cecum within the right lower quadrant of the abdomen at radiography is helpful in either diagnosing or excluding disease. These include malrotation (5,6), appendicitis (9,10), and intussusception (1–4). Misinterpretation of right lower quadrant air-filled sigmoid colon as cecum is perhaps most problematic in children who are suspected of having intussusception.
At most pediatric institutions, radiography remains the initial imaging examination performed in children who are suspected of having intussusception (1–4). With ileocolic intussusception, the cecum and ascending colon become gasless. Although there are many positive radiographic findings of intussusception (1–4), the identification of an air-filled cecum and ascending colon at radiography makes the diagnosis less likely. At many institutions, radiographic evaluation of the child suspected of having an intussusception includes abdominal radiography performed with the patient in the prone or left lateral decubitus position to maximize the chance of identifying an air-filled cecum and ascending colon (10,11). When evaluating such images, it should be considered that gas-filled colon within the right lower quadrant may be sigmoid colon.
It was our initial assumption that infants would have a higher frequency of sigmoid colon position within the right lower quadrant than would older children and that this frequency would decrease with increasing age. Since the sigmoid colon is normally positioned on the left side of the body in most young adults, there is a transition from right to left with increasing age. However, in children 5 years of age or younger (the population addressed in this study), there was no significant correlation between increasing age and decreasing frequency of right lower quadrant position. The age at which the frequency of right lower quadrant position of the sigmoid colon begins to decrease most likely is greater than 5 years. Older children were not included in this study; this may be the subject of further investigation.
One limitation of this study was that all enema examinations were ordered for clinical indications. Therefore, although a majority of the resultant radiographs (78%) showed normal findings, the subject population did not completely represent a healthy population. However, we think that it is unlikely that the frequency of right lower quadrant sigmoid colon position in the study population differs from the frequency that would be seen in asymptomatic children. For ethical reasons, it is unlikely that fluoroscopic enema examinations would ever be performed to study the normal anatomy of healthy young children. Enema examinations in children with underlying processes that may have changed the position of the sigmoid colon, which include malrotation, abdominal mass, or previous surgery, were not included in the study. Efforts were made to create a study population that would reflect healthy individuals. In addition, when only the 131 patients with normal enema studies were considered, 63 (48%) patients had sigmoid colon within the right lower quadrant.
In conclusion, the sigmoid colon is often positioned within the right lower quadrant in young children. We did not address potential explanations for this age-related anatomic variation. Knowledge of this high frequency should reduce the likelihood of misinterpreting air within a redundant right-sided sigmoid colon as air within the cecum in children being examined for a suspected abnormality.
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FOOTNOTES
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Author contributions: Guarantors of integrity of entire study, D.J.F., L.F.D.; study concepts and design, D.J.F., L.F.D.; definition of intellectual content, L.F.D.; literature research, D.J.F., L.F.D.; clinical studies, D.J.F., L.F.D.; data acquisition and analysis, D.J.F., L.F.D.; statistical analysis, D.J.F., L.F.D.; manuscript preparation, L.F.D.; manuscript editing and revision/review, D.J.F., L.F.D.; manuscript final version approval, L.F.D.
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ABSTRACT
INTRODUCTION
