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Infantile hypertrophic pyloric stenosis — Diagnosis from the pyloric muscle index
ClinicalRadiology(1988) 38, 625-627
Infantile Hypertrophic Pyloric Stenosis- Diagnosis from the Pyloric Muscle Index R. A. C A R V E R , M. O K O R I E * , G. M. S T E I N E R and J. A. S. D I C K S O N *
Departments of Radiology and *Surgery, Children's Hospital, Sheffield Measurements of pyloric length, diameter and muscle thickness were made from ultrasound images of 39 babies, 21 of w h o m were subsequently found at operation to have infantile hypertrophic pyioric stenosis. From these measurements, the volume of pyloric muscle in cm 3 was estimated for each case and divided by the body weight in kilograms. The resulting pyloric muscle index proved to be a much more reliable guide to the diagnosis of pyloric stenosis than any of the individual measurements or the volume estimation alone.
The pyloric muscle volume was estimated by assuming that it formed a hollow cylinder (Fig. 3). The formula for the volume of a cylinder is ~R2L, where R is the radius and L is the length. The volume of a hollow cylinder is the volume of the cylinder less the volume of the central core. Substituting the values in Fig. 3, the formula becomes V4~D2L-gz'L ( ½ D - T ) 2 = 1/4yrD2L- 1/4JrD2L + J r D T L - J r L T 2 =~TL (D-T)
Ultrasound examination is now a well established technique in the investigation of infants with suspected hypertrophic pyloric stenosis. Previous publications have a t t e m p t e d to define normal and abnormal ranges for m e a s u r e m e n t s of length, breadth and muscle thickness of the pylorus, and have demonstrated an overlap between these ranges for all three measurements. Thus there are still grounds for uncertainty in borderline cases. In our study, we have attempted to estimate pyloric volume from these three measurements and correlate this with body weight.
PATIENTS AND M E T H O D S Forty-one babies up to 6 months old were examined, all with a history of vomiting. In some cases the clinical diagnosis of infantile hypertrophic pyloric stenosis was certain, in some uncertain, and in the remainder unlikely. In 21 of these babies, the diagnosis of hypertrophic pyloric stenosis was confirmed at operation. Of the remaining 20 babies, 18 either ceased vomiting or were treated conservatively and it was assumed that they did not have infantile hypertrophic pyloric stenosis. Of the other two babies, one was vomiting following a diaphragmatic hernia repair and later died, and the other was subsequently found to have Hirschsprung's disease. It was felt that these babies could not be included in the group of normals. Ultrasound examination was performed by a radiologist, either a consultant or a senior registrar, or a radiographer with special expertise in ultrasound. A 7.5 M H z realtime sector scanner was used. The axis of the pylorus varied but could readily be found by scanning the right hypochondrium, showing on transverse section of the pylorus the well known 'target' appearance (Fig. l). The central bright core represents the mucosa and submucosa which is surrounded by a less echogenic ring of pyloric muscle. Rotation of the p r o b e through 90 ° produces a longitudinal image of the pylorus (Fig. 2). The length, breadth, and muscle thickness were measured, preferably f r o m a single longitudinal image. Each baby was weighed on the day of the examination.
Fig. 1- Oblique ultrasound scan of the right hypochondriumshowing a transverse section of a hypertrophied pylorus (arrowheads).
Fig. 2 - Oblique ultrasound scan of the right hypochondrium, the probe having been rotated through 90° from Fig. 1, to show a longitudinal section of the pylorus (arrowheads) and gas in the pyloric antrum (curved arrow). The straight arrow shows the liver.
626
CLINICAL R A D I O L O G Y
(o) Length
3.0
r I
2.5
I
*•
2,0
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-
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r
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-
?
.,,.'.... "7" t
I.©
I
(c) Muscle thickness
{b) Diameter
•ooZe•
0.5
-F" ©
I
I
I
I
Normal
IHPS
Normal
IHPS
I
Normal
IHPs
(a) (f) Muscular hypertrophy (e) Pyloric muscle index
(d) Pyioric volume
Fig. 3 - Diagram depicting the pyloric muscle as a hollow cylinder. L=Length; D=Diameter; T=Muscle Thickness.
1.5
5
-1-
5
RESULTS
4
The results are shown in Table 1 and in Fig. 4. The linear measurements obtained ultrasonically were found to correlate very closely with those made at surgery i n the operated cases; the surgeon did not have prior knowledge of the ultrasound findings. The pyloric muscle index was obtained by dividing the pyloric volume in cubic centimetres by the body weight in kilograms. The muscular hypertrophy index (Gonzalez de Orbe et al., 1986) was also calculated using the formula 2T/D (Fig. 3). Mean values and standard deviations were calculated for all six sets of figures. It can be seen from Table 1 and Fig. 4 that there is overlap between the normal and abnormal measurements for all three linear measurements, the muscular hypertrophy index, and for volume estimation. Furthermore, the mean value plus one standard deviation for all five normal ranges lies within or close to the respective abnormal range. However, there is clear separation between the normal and abnormal ranges for the pyloric muscle index, and the normal mean value plus three standard deviations (0.33) still lies below the abnormal range (0.46 to 1.26).
Table 1 - Results of measurements of pyioruses by ultrasound Measurement Group
Range
Mean
Standard Deviation
Length
1.0-1.6 cm 1.5-2.6 cm 0.7-1.6 cm 1.1-1.8 cm 0.1-0.3 cm 0.3-0.6 cm 0.26--1.96 c m 3 1.50-4.90 cm 3 0.08-0,28 0.46-1.26 0.25-0.86 0.40-0.92
1.27 1.93 1.01 1.49 0.23 0.42 0.76 2.72 0.15 0.81 0.48 0.57
0.28 0.36 0.25 0.17 0.06 0.09 0,52 1.00 0.06 0.24 0.15 0.12
Normal Pyloric stenosis Diameter Normal Pyloric stenosis Muscle Normal Thickness Pyloric stenosis Volume Normal Pyloric stenosis Pyloric Normal Muscle index Pyloric stenosis Muscular Normal Hypertrophy Pyloric stenosis Index
cm cm cm cm cm cm cm 3 cm 3
cm cm cm cm cm cm cm 3 cm 3
;•
index
1.2 1.0 0.8
1.0
T •oo
•
~3
0.6
I
--
eeo•
.,';5. $
0.5
+
I
+ 0
•
• o•
|
:° 2
•
0.4
~
0.2
__
eoee
*o"
i
I
Normal
I HPS
©
-r-
0
Normal
I HPS
~
I
Normal
IHPS
(b) Fig. 4 - Scatter diagrams of normal and abnormal ranges for (a) the three linear measurements and (b) the pyloric volumes, pyloric muscle indices and muscular hypertrophy indices. The mean values and the means _+2 standard deviations are marked on. IHPS=Infantile Hypertrophic Pylorie Stenosis.
DISCUSSION Ultrasound examination of the infant pylorus was first described by Teele and Smith (1977). Since then, there has been much published regarding normal and abnormal measurements of the pylorus. Some authors have attempted to define the upper limits of normal of 1.5 cm for diameter (Strauss et al., 1981; Pilling, 1983; Ball et al., 1983) or of 0.4 cm for muscle thickness (Blumhagen and Coombs, 1981; Ball et al., 1983); consequently, all series contained false positives or false negatives. Others defined normal and abnormal ranges for muscle thickness (Blumhagen and Noble, 1983) or for muscle thickness, diameter, and length (Sauerbrei and Paloschi, 1983; Grail et al., 1984; Cremin, 1985). All these series produced overlapping normal and abnormal ranges. Our results agreed with these findings (Table 1, Fig. 4a, b, c). Whilst performing these examinations, we observed that the pylorus changes shape, so that individual measurements must vary. However, the total volume of muscle must remain constant. Furthermore, pyloric stenosis can be present from birth up to several months
INFANTILEPYLOR1CSTENOSIS of age, and therefore during a period of significant growth; it therefore s e e m e d a p p r o p r i a t e to correlate pyloric v o l u m e with b o d y weight. R e g a r d i n g the pyloric muscle as a hollow cylinder is rather a crude assumption, but we considered it w o u l d be sufficiently accurate for our needs. Estimations of pyloric v o l u m e p r o d u c e d n o r m a l and a b n o r m a l ranges which o v e r l a p p e d in a similar fashion to those of the linear m e a s u r e m e n t s (Fig. 4). H o w e v e r the pyloric v o l u m e / b o d y weight ratio, which we have designated the pyloric muscle index p r o d u c e d clearly separated n o r m a l and a b n o r m a l ranges (Fig. 4e). F u r t h e r m o r e , because the n o r m a l m e a n value plus three standard deviations (0.33) still lies below the a b n o r m a l range (0.46 to 1.26), the chance of a n o r m a l pylorus having a value of m o r e than 0.33 is 0.15%. Since we started this project, the muscular h y p e r t r o p h y index has b e e n described ( G o n z a l e z de O r b e et al., 1986) as less than 0.5 in n o r m a l babies, and m o r e than 0.5 in infantile h y p e r t r o p h i c pytoric stenosis. O u r results did not agree with these findings (Table 1, Fig. 4f), p r e s u m a b l y because the pylorus changes shape. W e conclude that estimation of the pyloric muscle index is a reliable guide to the diagnosis of infantile h y p e r t r o p h i c pyloric stenosis. If this index is less than 0.4, the pylorus is n o r m a l , and if m o r e than 0.4, the diagnosis of h y p e r t r o p h i c pyloric stenosis can be m a d e .
Acknowledgements. Our thanks to Miss Anne Thompson for performing many of the scans, to Mrs Yvonne Steel for typing the
627
manuscript, and to the Medical Illustration Department for preparing the illustrations.
REFERENCES
Ball, TI, Atkinson, GO & Gay, Jr, BB (1983). Ultrasound diagnosis of hypertrophic pyloric stenosis: real-time application and the demonstration of a new sonographic sign. Radiology, 147, 499-502. Blumhagen, JD & Coombs, JB (1981). Ultrasound in the diagnosis of hypertrophic pyloric stenosis. Journal of Clinical Ultrasound, 9, 289-292. Blumhagen, JD & Noble, HGS (1983). Muscle thickness in hypertrophic pyloric stenosis: sonographic determination. American Journal of Roentgenology, 140, 221-223. Cremin, BJ (1985). Real time ultrasonic evaluation of the paediatric abdomen: technique and anatomical variations. A personal view. British Journal of Radiology, 58, 85%868. Gonzalez de Orbe, G, Pulpeiro, JR, Collado, J, Serrano, C, Miralles, M & y Martinez, A (1986). A new finding in ultrasound diagnosis of hypertrophic pyloric stenosis: the muscular hypertrophy index. (Abstract). Pediatric Radiology, 16, 117-118. Graif, M, Itzchak, Y, Avigad, I, Strauss, S & Ben-Ami, T (1984). The pylorus in infancy: overall sonographic assessment. Pediatric Radiology, 14, 14-17. Pilling, DW (1983) Infantile hypertrophic pyloric stenosis: a fresh approach to the diagnosis. Clinical Radiology, 34, 51-53. Sauerbrei, EE & Paloschi, GGB (1983) The ultrasonic features of hypertrophic pyloric stenosis, with emphasis on the postoperative appearance. Radiology, 147, 503-506. Strauss, S, Itzchak, Y, Manor, A, Heyman, Z & Graif, M (1981). Sonography of hypertrophic pyloric stenosis. American Journal of Roentgenology, 136, 1057-1058. Teele, RL & Smith, EH (1977). Ultrasound in the Diagnosis of Idiopathic Hypertrophic Pyloric Stenosis. The New England Journal of Medicine, 296, 1149-1150.
Infantile Hypertrophic Pyloric Stenosis- Diagnosis from the Pyloric Muscle Index R. A. C A R V E R , M. O K O R I E * , G. M. S T E I N E R and J. A. S. D I C K S O N *
Departments of Radiology and *Surgery, Children's Hospital, Sheffield Measurements of pyloric length, diameter and muscle thickness were made from ultrasound images of 39 babies, 21 of w h o m were subsequently found at operation to have infantile hypertrophic pyioric stenosis. From these measurements, the volume of pyloric muscle in cm 3 was estimated for each case and divided by the body weight in kilograms. The resulting pyloric muscle index proved to be a much more reliable guide to the diagnosis of pyloric stenosis than any of the individual measurements or the volume estimation alone.
The pyloric muscle volume was estimated by assuming that it formed a hollow cylinder (Fig. 3). The formula for the volume of a cylinder is ~R2L, where R is the radius and L is the length. The volume of a hollow cylinder is the volume of the cylinder less the volume of the central core. Substituting the values in Fig. 3, the formula becomes V4~D2L-gz'L ( ½ D - T ) 2 = 1/4yrD2L- 1/4JrD2L + J r D T L - J r L T 2 =~TL (D-T)
Ultrasound examination is now a well established technique in the investigation of infants with suspected hypertrophic pyloric stenosis. Previous publications have a t t e m p t e d to define normal and abnormal ranges for m e a s u r e m e n t s of length, breadth and muscle thickness of the pylorus, and have demonstrated an overlap between these ranges for all three measurements. Thus there are still grounds for uncertainty in borderline cases. In our study, we have attempted to estimate pyloric volume from these three measurements and correlate this with body weight.
PATIENTS AND M E T H O D S Forty-one babies up to 6 months old were examined, all with a history of vomiting. In some cases the clinical diagnosis of infantile hypertrophic pyloric stenosis was certain, in some uncertain, and in the remainder unlikely. In 21 of these babies, the diagnosis of hypertrophic pyloric stenosis was confirmed at operation. Of the remaining 20 babies, 18 either ceased vomiting or were treated conservatively and it was assumed that they did not have infantile hypertrophic pyloric stenosis. Of the other two babies, one was vomiting following a diaphragmatic hernia repair and later died, and the other was subsequently found to have Hirschsprung's disease. It was felt that these babies could not be included in the group of normals. Ultrasound examination was performed by a radiologist, either a consultant or a senior registrar, or a radiographer with special expertise in ultrasound. A 7.5 M H z realtime sector scanner was used. The axis of the pylorus varied but could readily be found by scanning the right hypochondrium, showing on transverse section of the pylorus the well known 'target' appearance (Fig. l). The central bright core represents the mucosa and submucosa which is surrounded by a less echogenic ring of pyloric muscle. Rotation of the p r o b e through 90 ° produces a longitudinal image of the pylorus (Fig. 2). The length, breadth, and muscle thickness were measured, preferably f r o m a single longitudinal image. Each baby was weighed on the day of the examination.
Fig. 1- Oblique ultrasound scan of the right hypochondriumshowing a transverse section of a hypertrophied pylorus (arrowheads).
Fig. 2 - Oblique ultrasound scan of the right hypochondrium, the probe having been rotated through 90° from Fig. 1, to show a longitudinal section of the pylorus (arrowheads) and gas in the pyloric antrum (curved arrow). The straight arrow shows the liver.
626
CLINICAL R A D I O L O G Y
(o) Length
3.0
r I
2.5
I
*•
2,0
o..~,• -
-
B.
E i.5
r
__" .....
•000•
oo•• o0o
-
?
.,,.'.... "7" t
I.©
I
(c) Muscle thickness
{b) Diameter
•ooZe•
0.5
-F" ©
I
I
I
I
Normal
IHPS
Normal
IHPS
I
Normal
IHPs
(a) (f) Muscular hypertrophy (e) Pyloric muscle index
(d) Pyioric volume
Fig. 3 - Diagram depicting the pyloric muscle as a hollow cylinder. L=Length; D=Diameter; T=Muscle Thickness.
1.5
5
-1-
5
RESULTS
4
The results are shown in Table 1 and in Fig. 4. The linear measurements obtained ultrasonically were found to correlate very closely with those made at surgery i n the operated cases; the surgeon did not have prior knowledge of the ultrasound findings. The pyloric muscle index was obtained by dividing the pyloric volume in cubic centimetres by the body weight in kilograms. The muscular hypertrophy index (Gonzalez de Orbe et al., 1986) was also calculated using the formula 2T/D (Fig. 3). Mean values and standard deviations were calculated for all six sets of figures. It can be seen from Table 1 and Fig. 4 that there is overlap between the normal and abnormal measurements for all three linear measurements, the muscular hypertrophy index, and for volume estimation. Furthermore, the mean value plus one standard deviation for all five normal ranges lies within or close to the respective abnormal range. However, there is clear separation between the normal and abnormal ranges for the pyloric muscle index, and the normal mean value plus three standard deviations (0.33) still lies below the abnormal range (0.46 to 1.26).
Table 1 - Results of measurements of pyioruses by ultrasound Measurement Group
Range
Mean
Standard Deviation
Length
1.0-1.6 cm 1.5-2.6 cm 0.7-1.6 cm 1.1-1.8 cm 0.1-0.3 cm 0.3-0.6 cm 0.26--1.96 c m 3 1.50-4.90 cm 3 0.08-0,28 0.46-1.26 0.25-0.86 0.40-0.92
1.27 1.93 1.01 1.49 0.23 0.42 0.76 2.72 0.15 0.81 0.48 0.57
0.28 0.36 0.25 0.17 0.06 0.09 0,52 1.00 0.06 0.24 0.15 0.12
Normal Pyloric stenosis Diameter Normal Pyloric stenosis Muscle Normal Thickness Pyloric stenosis Volume Normal Pyloric stenosis Pyloric Normal Muscle index Pyloric stenosis Muscular Normal Hypertrophy Pyloric stenosis Index
cm cm cm cm cm cm cm 3 cm 3
cm cm cm cm cm cm cm 3 cm 3
;•
index
1.2 1.0 0.8
1.0
T •oo
•
~3
0.6
I
--
eeo•
.,';5. $
0.5
+
I
+ 0
•
• o•
|
:° 2
•
0.4
~
0.2
__
eoee
*o"
i
I
Normal
I HPS
©
-r-
0
Normal
I HPS
~
I
Normal
IHPS
(b) Fig. 4 - Scatter diagrams of normal and abnormal ranges for (a) the three linear measurements and (b) the pyloric volumes, pyloric muscle indices and muscular hypertrophy indices. The mean values and the means _+2 standard deviations are marked on. IHPS=Infantile Hypertrophic Pylorie Stenosis.
DISCUSSION Ultrasound examination of the infant pylorus was first described by Teele and Smith (1977). Since then, there has been much published regarding normal and abnormal measurements of the pylorus. Some authors have attempted to define the upper limits of normal of 1.5 cm for diameter (Strauss et al., 1981; Pilling, 1983; Ball et al., 1983) or of 0.4 cm for muscle thickness (Blumhagen and Coombs, 1981; Ball et al., 1983); consequently, all series contained false positives or false negatives. Others defined normal and abnormal ranges for muscle thickness (Blumhagen and Noble, 1983) or for muscle thickness, diameter, and length (Sauerbrei and Paloschi, 1983; Grail et al., 1984; Cremin, 1985). All these series produced overlapping normal and abnormal ranges. Our results agreed with these findings (Table 1, Fig. 4a, b, c). Whilst performing these examinations, we observed that the pylorus changes shape, so that individual measurements must vary. However, the total volume of muscle must remain constant. Furthermore, pyloric stenosis can be present from birth up to several months
INFANTILEPYLOR1CSTENOSIS of age, and therefore during a period of significant growth; it therefore s e e m e d a p p r o p r i a t e to correlate pyloric v o l u m e with b o d y weight. R e g a r d i n g the pyloric muscle as a hollow cylinder is rather a crude assumption, but we considered it w o u l d be sufficiently accurate for our needs. Estimations of pyloric v o l u m e p r o d u c e d n o r m a l and a b n o r m a l ranges which o v e r l a p p e d in a similar fashion to those of the linear m e a s u r e m e n t s (Fig. 4). H o w e v e r the pyloric v o l u m e / b o d y weight ratio, which we have designated the pyloric muscle index p r o d u c e d clearly separated n o r m a l and a b n o r m a l ranges (Fig. 4e). F u r t h e r m o r e , because the n o r m a l m e a n value plus three standard deviations (0.33) still lies below the a b n o r m a l range (0.46 to 1.26), the chance of a n o r m a l pylorus having a value of m o r e than 0.33 is 0.15%. Since we started this project, the muscular h y p e r t r o p h y index has b e e n described ( G o n z a l e z de O r b e et al., 1986) as less than 0.5 in n o r m a l babies, and m o r e than 0.5 in infantile h y p e r t r o p h i c pytoric stenosis. O u r results did not agree with these findings (Table 1, Fig. 4f), p r e s u m a b l y because the pylorus changes shape. W e conclude that estimation of the pyloric muscle index is a reliable guide to the diagnosis of infantile h y p e r t r o p h i c pyloric stenosis. If this index is less than 0.4, the pylorus is n o r m a l , and if m o r e than 0.4, the diagnosis of h y p e r t r o p h i c pyloric stenosis can be m a d e .
Acknowledgements. Our thanks to Miss Anne Thompson for performing many of the scans, to Mrs Yvonne Steel for typing the
627
manuscript, and to the Medical Illustration Department for preparing the illustrations.
REFERENCES
Ball, TI, Atkinson, GO & Gay, Jr, BB (1983). Ultrasound diagnosis of hypertrophic pyloric stenosis: real-time application and the demonstration of a new sonographic sign. Radiology, 147, 499-502. Blumhagen, JD & Coombs, JB (1981). Ultrasound in the diagnosis of hypertrophic pyloric stenosis. Journal of Clinical Ultrasound, 9, 289-292. Blumhagen, JD & Noble, HGS (1983). Muscle thickness in hypertrophic pyloric stenosis: sonographic determination. American Journal of Roentgenology, 140, 221-223. Cremin, BJ (1985). Real time ultrasonic evaluation of the paediatric abdomen: technique and anatomical variations. A personal view. British Journal of Radiology, 58, 85%868. Gonzalez de Orbe, G, Pulpeiro, JR, Collado, J, Serrano, C, Miralles, M & y Martinez, A (1986). A new finding in ultrasound diagnosis of hypertrophic pyloric stenosis: the muscular hypertrophy index. (Abstract). Pediatric Radiology, 16, 117-118. Graif, M, Itzchak, Y, Avigad, I, Strauss, S & Ben-Ami, T (1984). The pylorus in infancy: overall sonographic assessment. Pediatric Radiology, 14, 14-17. Pilling, DW (1983) Infantile hypertrophic pyloric stenosis: a fresh approach to the diagnosis. Clinical Radiology, 34, 51-53. Sauerbrei, EE & Paloschi, GGB (1983) The ultrasonic features of hypertrophic pyloric stenosis, with emphasis on the postoperative appearance. Radiology, 147, 503-506. Strauss, S, Itzchak, Y, Manor, A, Heyman, Z & Graif, M (1981). Sonography of hypertrophic pyloric stenosis. American Journal of Roentgenology, 136, 1057-1058. Teele, RL & Smith, EH (1977). Ultrasound in the Diagnosis of Idiopathic Hypertrophic Pyloric Stenosis. The New England Journal of Medicine, 296, 1149-1150.