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Ultrasound diagnosis of hypertrophic pyloric stenosis
January 1983 The Journal o f P E D I A T R I C S
23
Ultrasound diagnosis of hypertrophic pyloric stenosis Thirty infants presenting with vomiting were examined sonographically. In 18 o f these patients, a hypoechoic mass medial to the gallbladder and anterior to the right kidney was demonstrated. The mass measured more than 1 cm in diameter in all cases, with an average o f 1.7 cm, and was interpreted as representing the hypertrophied muscle mass in pyloric stenosis. Sixteen o f these infants had subsequent confirmation o f this diagnosis by upper gastrointestinal tract examination and surgery. In two infants, both o f whom had a small-diameter mass, the upper gastrointestinal tract study showed an atypical appearing pyloric canal," these two infants were thought to have atypical hypertrophic pyloric stenosis. Of importance technically is operator experience and patience and the use o f different patient positions and even real-time imaging for completeness. Potential pitfalls include the fluid-filled duodenal bulb and gastric antrum, which cause a false positive diagnosis, and obscuration o f a lesion by overlying bowel gas, which leads to a false negative diagnosis.
Tuenchit Khamapirad, M.D., and Patricia A. Athey, M.D. Houston, Texas
HYPERTROPHIC PYLORIC STENOSIS was diagnosed by ultrasound in five patients by Teele and Smith ~ in 1977. Since then two additional reports have confirmed the value of ultrasound in this entity?,3 This communication reports our experience in the diagnosis of hypertrophic pyloric stenosis using ultrasound. S U B J E C T S AND M E T H O D S During the past eight months we examined ultrasonically 30 patients clinically suspected of having hypertrophic pyloric stenosis. The degree of clinical suspicion varied widely from case to case. The ages of these patients ranged from 1 to 6 weeks, and all had a history of vomiting, generally projectile in nature. The ultrasound examination was performed with the use of digital gray scale static equipment and a 5 MHz 6 mm width transducer focused at 2 cm. The infants were manually restrained but not sedated; the use of a pacifier was extremely helpful in obtaining satisfactory cooperation. Transverse and longitudinal images were achieved with the infants in the supine position, and additional views From the Department o f Radiology, Baylor College o f Medicine, and Ben Taub General Hospital. Reprint address." Patricia A. Athey, M.D., Baylor College o f Medicine, Department o f Radiology, 1200 Moursund, Houston, TX 77030.
0022-3476/83/010023+04500.40/0 9 1983 The C. V. Mosby Co.
were occasionally taken with the infants in a left lateral decubitus position. Following the ultrasound examination, an upper gastrointestinal tract series was obtained in all patients. RESULTS The ultrasound diagnosis of hypertrophic pyloric stenosis was made by means of the following criteria: (1) demonstration of a hypoechoic mass located medial to the gallbladder, anterior to the right kidney, and lateral to the head of the pancreas on transverse scans and posteroinferior to the gallbladder on longitudinal scans (Fig. 1, A and B), (2) mass diameter 1 cm or greater and containing a central echo that was round or stellate, and (3) continuation of the hypoechoic mass with the gastric antrum on subsequent scans. These criteria were fulfilled in 18 of the 30 patients examined, and they were considered positive for hypertrophic pyloric stenosis. The diameter of the hypoechoic mass ranged from 1.2 to 2.2 cm with an average of 1.7 cm. In 16 of these patients, the upper gastrointestinal tract series was also considered positive for hypertrophic pyloric stenosis (Fig. 1, C), and this diagnosis was confirmed surgically. In the other two infants who had a mass by ultrasound, the barium study showed an atypical looking pyloric canal that was not completely obstructed at fluo-
Vol. 102, No. l, pp. 23-26
24
Khamapirad and Athey
The Journal of Pediatrics January 1983
Fig. 1. A, Transverse sonogram demonstrating mass of hypertrophic pyloric stenosis (arrowheads) medial to gallbladder (G) and anterior to right kidney (K). B, Longitudinal sonogram demonstrating typical mass (arrowheads) located posteroinferior to gallbladder (G). L-liver C, Classic findings of hypertrophic pyloric stenosis on upper gastrointestinal tract examination.
roscopy (Fig. 2, A and B). In both of these patients, the mass at ultrasound measured 1.2 cm in diameter. One of these patients underwent surgery, which revealed a small pyloric muscle mass. The other infant was treated conservatively and became asymptomatic. In 12 patients, no mass could be demonstrated ultrasonically, and this finding correlated well with a negative upper gastrointestinal tract series. None of these patients underwent surgery. Among these negative cases, the normal pyloric ring was occasionally demonstrated. It was similar in appearance to the mass of hypertrophic pyloric stenosis but was less than 1 cm in diameter. In two of these normal patients, sonolucent structures containing punctate echogenicities were seen in the same location as the mass of hypertrophic pyloric stenosis, but these were believed to represent fluid-filled gastric a n t r u m or duodenal bulb containing air bubbles (Fig. 3).
DISCUSSION In general, the diagnosis of hypertrophic pyloric stenosis can be made with confidence on the basis of the history and physical examination alone? When the clinical findings are equivocal, the diagnosis can be confirmed roentgenographically by means of an upper gastrointestinal tract series? Since the initial report of the use of ultrasound in the diagnosis of hypertrophic pyloric stenosis] two other groups have published data attesting to the accuracy of the ultrasonic diagnosis of this entity. 2,3 As a confirmatory procedure, ultrasound is advantageous over fluoroscopy in that it does not utilize ionizing radiation and does not introduce the hazard of barium aspiration. Ultrasound visualizes the hypertrophic muscle directly as a hypoechoic mass with an echogenic center. Such a bull's-eye or target appearance has been frequently described and attributed to a bowel lesion with thickened walls caused by inflamma-
Volume 102 Number 1
Hypertrophic pyloric stenosis
25
Fig. 2. A. Longitudinal sonogram in infant with atypical hypertrophic pyloric stenosis demonstrating small muscle mass (arrowheads) 1.2 cm in diameter. B, L-liver. Upper gastrointestinal tract study in same infant, demonstrating atypical appearing pyloric canal. tion or neoplasm. 6 However, in the appropriate clinical setting (i.e., the infant with vomiting) such a mass in the expected location of the pylorus is typical of hypertrophic pyloric stenosis. Previous reports have cited mass diameters ranging from 1.8 to 2.8 cm 1 and 1.5 to 3 cm, 3 respectively, as being diagnostic for hypertrophic pyloric stenosis. Another way of making this measurement is to assess the thickness of each wall of the hypoechoic ring; this was found to be 4 mm or greater by B!oomhagen and Coombs. 2 In our series the diameter of the hypertrophic muscle mass ranged from 1.2 to 2.2 cm. Taking into consideration all of the above data, it is reasonable to establish a diameter of 1.5 cm or greater as being diagnostic of hypertrophic pyloric stenosis. Atypical muscle hypertrophy in pyloric stenosis is an entity in which the symmetrically elongated pyloric canal of hypertrophic pyloric stenosis is not present; rather, there is a variation in the appearance of the pyloric canal caused by asymmetric muscle hypertrophy. 7 In addition the obstruction to the flow of barium through this lesion is incomplete. If the radiologist is unfamiliar with this entity, it can be missed at fluoroscopy. The demonstration of a small hypoechoic muscle mass by ultrasound would aid in the diagnosis in these cases. Because of our experience with two cases of atypical hypertrophy of pyloric stenosis, in which measurements of 1.2 cm were obtained, we would suggest that a hypoechoic mass of 1 to 1.4 cm diameter be
Fig. 3. Fluid collection containing punctate densities medial to gallbladder (G) representing fluid and air bubbles in duodenum (D). L-liver.
considered suggestive of either hypertrophic pyloric stenosis or atypical hypertrophy; in such cases further evaluation with an upper gastrointestinal tract series would be required. The technical aspects of ultrasound imaging in these infants are very important. Obtaining adequate studies requires patience and experience. The use of a pacifier is mandatory. In many cases, transverse and longitudinal
26
Khamapirad and Athey
supine scans were inadequate for diagnosis and were supplemented with additional scans with the patient in the left lateral decubitus position. Real-time imaging can also be of considerable assistance, particularly in shortening the examination time in an uncooperative infant. False negative scans may be caused by bowel gas obscuring the lesion. Conversely, the fluid-filled duodenal bulb or gastric antrum can be a potential source of a false positive diagnosis, although we did not encounter either in our series. We believe that in the infant clinically suspected of having hypertrophic pyloric stenosis, ultrasound rather than an upper gastrointestinal tract series can be used as a confirmatory test. If a typical hypoechoic mass is demonstrated and has a diameter of 1.5 cm or greater, no further confirmation is needed. If, however, a mass of 1 to 1.4 cm is demonstrated, an upper gastrointestinal tract series will be helpful in further evahiation, especially in cases of atypical hypertrophy. If no mass is seen ultrasonically, it will still be necessary to obtain an upper gastrointestinal tract series to exclude other conditions such as pylorospasm, congenital intestinal obstruction, malrotation, duplication, and gastroesophageal reflux as a cause for the clinical symptoms?. 8.9
The Journal of Pediatrics January 1983
REFERENCES
1. Teele RL, and Smith EH: Ultrasound in the diagnosis of idiopathic hypertrophic pyloric stenosis, N Engl J Med 296:1149, 1977. 2. Bloomhagen JD, and Coombs JB: Ultrasound in the diagnosis of hypertrophic pyloric stenosis, J Clin Ultrasound 9:289, 198l. 3. Strauss S, Itzchak Y, Manor A, Heyman Z, and Graif M: Sonography of hypertrophic pyloric stenosis, A JR 136:1057, 1981. 4. Scharli A, Seiber WK, and Kiesewetter WB: Hypertrophic pyloric stenosis at the Children's Hospital of Pittsburgh from 1912 to 1967: A critical review of current problems and complications, J Pediatr Surg 4:108, 1969. 5. Singleton EB, Wagner ML, and Dutton RV: Radiology of the alimentary tract in infants and children, ed 2, Philadelphia, 1977, W. B. Saunders Company, pp 125-132. 6. Morgan CL, Trought WS, Oddson TA, Clark WM, and Rice RP: Ultrasound patterns of disorders afflicting the gastrointestinal tract, Radiology 135:129, 1980. 7. Swischuk LE, Hayden CK Jr, and Tyson KR: Atypical muscle hypertrophy in pyloric stenosis, A JR 134:481, 1980. 8. Kammerer GT: Duplication of the stomach resembling hypertrophic pyloric stenosis, JAMA 207:2101, 1969. 9. Matsumoto Y, Kawai K, and Kimura K: Aberrant pancreas causing pyloric obstruction, Surgery 76:827, 1974.
23
Ultrasound diagnosis of hypertrophic pyloric stenosis Thirty infants presenting with vomiting were examined sonographically. In 18 o f these patients, a hypoechoic mass medial to the gallbladder and anterior to the right kidney was demonstrated. The mass measured more than 1 cm in diameter in all cases, with an average o f 1.7 cm, and was interpreted as representing the hypertrophied muscle mass in pyloric stenosis. Sixteen o f these infants had subsequent confirmation o f this diagnosis by upper gastrointestinal tract examination and surgery. In two infants, both o f whom had a small-diameter mass, the upper gastrointestinal tract study showed an atypical appearing pyloric canal," these two infants were thought to have atypical hypertrophic pyloric stenosis. Of importance technically is operator experience and patience and the use o f different patient positions and even real-time imaging for completeness. Potential pitfalls include the fluid-filled duodenal bulb and gastric antrum, which cause a false positive diagnosis, and obscuration o f a lesion by overlying bowel gas, which leads to a false negative diagnosis.
Tuenchit Khamapirad, M.D., and Patricia A. Athey, M.D. Houston, Texas
HYPERTROPHIC PYLORIC STENOSIS was diagnosed by ultrasound in five patients by Teele and Smith ~ in 1977. Since then two additional reports have confirmed the value of ultrasound in this entity?,3 This communication reports our experience in the diagnosis of hypertrophic pyloric stenosis using ultrasound. S U B J E C T S AND M E T H O D S During the past eight months we examined ultrasonically 30 patients clinically suspected of having hypertrophic pyloric stenosis. The degree of clinical suspicion varied widely from case to case. The ages of these patients ranged from 1 to 6 weeks, and all had a history of vomiting, generally projectile in nature. The ultrasound examination was performed with the use of digital gray scale static equipment and a 5 MHz 6 mm width transducer focused at 2 cm. The infants were manually restrained but not sedated; the use of a pacifier was extremely helpful in obtaining satisfactory cooperation. Transverse and longitudinal images were achieved with the infants in the supine position, and additional views From the Department o f Radiology, Baylor College o f Medicine, and Ben Taub General Hospital. Reprint address." Patricia A. Athey, M.D., Baylor College o f Medicine, Department o f Radiology, 1200 Moursund, Houston, TX 77030.
0022-3476/83/010023+04500.40/0 9 1983 The C. V. Mosby Co.
were occasionally taken with the infants in a left lateral decubitus position. Following the ultrasound examination, an upper gastrointestinal tract series was obtained in all patients. RESULTS The ultrasound diagnosis of hypertrophic pyloric stenosis was made by means of the following criteria: (1) demonstration of a hypoechoic mass located medial to the gallbladder, anterior to the right kidney, and lateral to the head of the pancreas on transverse scans and posteroinferior to the gallbladder on longitudinal scans (Fig. 1, A and B), (2) mass diameter 1 cm or greater and containing a central echo that was round or stellate, and (3) continuation of the hypoechoic mass with the gastric antrum on subsequent scans. These criteria were fulfilled in 18 of the 30 patients examined, and they were considered positive for hypertrophic pyloric stenosis. The diameter of the hypoechoic mass ranged from 1.2 to 2.2 cm with an average of 1.7 cm. In 16 of these patients, the upper gastrointestinal tract series was also considered positive for hypertrophic pyloric stenosis (Fig. 1, C), and this diagnosis was confirmed surgically. In the other two infants who had a mass by ultrasound, the barium study showed an atypical looking pyloric canal that was not completely obstructed at fluo-
Vol. 102, No. l, pp. 23-26
24
Khamapirad and Athey
The Journal of Pediatrics January 1983
Fig. 1. A, Transverse sonogram demonstrating mass of hypertrophic pyloric stenosis (arrowheads) medial to gallbladder (G) and anterior to right kidney (K). B, Longitudinal sonogram demonstrating typical mass (arrowheads) located posteroinferior to gallbladder (G). L-liver C, Classic findings of hypertrophic pyloric stenosis on upper gastrointestinal tract examination.
roscopy (Fig. 2, A and B). In both of these patients, the mass at ultrasound measured 1.2 cm in diameter. One of these patients underwent surgery, which revealed a small pyloric muscle mass. The other infant was treated conservatively and became asymptomatic. In 12 patients, no mass could be demonstrated ultrasonically, and this finding correlated well with a negative upper gastrointestinal tract series. None of these patients underwent surgery. Among these negative cases, the normal pyloric ring was occasionally demonstrated. It was similar in appearance to the mass of hypertrophic pyloric stenosis but was less than 1 cm in diameter. In two of these normal patients, sonolucent structures containing punctate echogenicities were seen in the same location as the mass of hypertrophic pyloric stenosis, but these were believed to represent fluid-filled gastric a n t r u m or duodenal bulb containing air bubbles (Fig. 3).
DISCUSSION In general, the diagnosis of hypertrophic pyloric stenosis can be made with confidence on the basis of the history and physical examination alone? When the clinical findings are equivocal, the diagnosis can be confirmed roentgenographically by means of an upper gastrointestinal tract series? Since the initial report of the use of ultrasound in the diagnosis of hypertrophic pyloric stenosis] two other groups have published data attesting to the accuracy of the ultrasonic diagnosis of this entity. 2,3 As a confirmatory procedure, ultrasound is advantageous over fluoroscopy in that it does not utilize ionizing radiation and does not introduce the hazard of barium aspiration. Ultrasound visualizes the hypertrophic muscle directly as a hypoechoic mass with an echogenic center. Such a bull's-eye or target appearance has been frequently described and attributed to a bowel lesion with thickened walls caused by inflamma-
Volume 102 Number 1
Hypertrophic pyloric stenosis
25
Fig. 2. A. Longitudinal sonogram in infant with atypical hypertrophic pyloric stenosis demonstrating small muscle mass (arrowheads) 1.2 cm in diameter. B, L-liver. Upper gastrointestinal tract study in same infant, demonstrating atypical appearing pyloric canal. tion or neoplasm. 6 However, in the appropriate clinical setting (i.e., the infant with vomiting) such a mass in the expected location of the pylorus is typical of hypertrophic pyloric stenosis. Previous reports have cited mass diameters ranging from 1.8 to 2.8 cm 1 and 1.5 to 3 cm, 3 respectively, as being diagnostic for hypertrophic pyloric stenosis. Another way of making this measurement is to assess the thickness of each wall of the hypoechoic ring; this was found to be 4 mm or greater by B!oomhagen and Coombs. 2 In our series the diameter of the hypertrophic muscle mass ranged from 1.2 to 2.2 cm. Taking into consideration all of the above data, it is reasonable to establish a diameter of 1.5 cm or greater as being diagnostic of hypertrophic pyloric stenosis. Atypical muscle hypertrophy in pyloric stenosis is an entity in which the symmetrically elongated pyloric canal of hypertrophic pyloric stenosis is not present; rather, there is a variation in the appearance of the pyloric canal caused by asymmetric muscle hypertrophy. 7 In addition the obstruction to the flow of barium through this lesion is incomplete. If the radiologist is unfamiliar with this entity, it can be missed at fluoroscopy. The demonstration of a small hypoechoic muscle mass by ultrasound would aid in the diagnosis in these cases. Because of our experience with two cases of atypical hypertrophy of pyloric stenosis, in which measurements of 1.2 cm were obtained, we would suggest that a hypoechoic mass of 1 to 1.4 cm diameter be
Fig. 3. Fluid collection containing punctate densities medial to gallbladder (G) representing fluid and air bubbles in duodenum (D). L-liver.
considered suggestive of either hypertrophic pyloric stenosis or atypical hypertrophy; in such cases further evaluation with an upper gastrointestinal tract series would be required. The technical aspects of ultrasound imaging in these infants are very important. Obtaining adequate studies requires patience and experience. The use of a pacifier is mandatory. In many cases, transverse and longitudinal
26
Khamapirad and Athey
supine scans were inadequate for diagnosis and were supplemented with additional scans with the patient in the left lateral decubitus position. Real-time imaging can also be of considerable assistance, particularly in shortening the examination time in an uncooperative infant. False negative scans may be caused by bowel gas obscuring the lesion. Conversely, the fluid-filled duodenal bulb or gastric antrum can be a potential source of a false positive diagnosis, although we did not encounter either in our series. We believe that in the infant clinically suspected of having hypertrophic pyloric stenosis, ultrasound rather than an upper gastrointestinal tract series can be used as a confirmatory test. If a typical hypoechoic mass is demonstrated and has a diameter of 1.5 cm or greater, no further confirmation is needed. If, however, a mass of 1 to 1.4 cm is demonstrated, an upper gastrointestinal tract series will be helpful in further evahiation, especially in cases of atypical hypertrophy. If no mass is seen ultrasonically, it will still be necessary to obtain an upper gastrointestinal tract series to exclude other conditions such as pylorospasm, congenital intestinal obstruction, malrotation, duplication, and gastroesophageal reflux as a cause for the clinical symptoms?. 8.9
The Journal of Pediatrics January 1983
REFERENCES
1. Teele RL, and Smith EH: Ultrasound in the diagnosis of idiopathic hypertrophic pyloric stenosis, N Engl J Med 296:1149, 1977. 2. Bloomhagen JD, and Coombs JB: Ultrasound in the diagnosis of hypertrophic pyloric stenosis, J Clin Ultrasound 9:289, 198l. 3. Strauss S, Itzchak Y, Manor A, Heyman Z, and Graif M: Sonography of hypertrophic pyloric stenosis, A JR 136:1057, 1981. 4. Scharli A, Seiber WK, and Kiesewetter WB: Hypertrophic pyloric stenosis at the Children's Hospital of Pittsburgh from 1912 to 1967: A critical review of current problems and complications, J Pediatr Surg 4:108, 1969. 5. Singleton EB, Wagner ML, and Dutton RV: Radiology of the alimentary tract in infants and children, ed 2, Philadelphia, 1977, W. B. Saunders Company, pp 125-132. 6. Morgan CL, Trought WS, Oddson TA, Clark WM, and Rice RP: Ultrasound patterns of disorders afflicting the gastrointestinal tract, Radiology 135:129, 1980. 7. Swischuk LE, Hayden CK Jr, and Tyson KR: Atypical muscle hypertrophy in pyloric stenosis, A JR 134:481, 1980. 8. Kammerer GT: Duplication of the stomach resembling hypertrophic pyloric stenosis, JAMA 207:2101, 1969. 9. Matsumoto Y, Kawai K, and Kimura K: Aberrant pancreas causing pyloric obstruction, Surgery 76:827, 1974.