Sonographic Appearances of Common Gut Pathology in Paediatric Patients: Comparison with Plain Abdominal Radiography

Transcription

1 3668 Radiographer Text 1/4/04 2:57 PM Page 11 The Radiographer vol. 51: Sonographic Appearances of Common Gut Pathology in Paediatric Patients: Comparison with Plain Abdominal Radiography Lino Piotto and Roger Gent ABSTRACT Even with the advent of more specialised imaging modalities such as fluoroscopic contrast examinations, CT and MRI, the plain abdominal radiograph remains the initial imaging modality in investigating the signs and symptoms of suspected gut pathology. However, ultrasound is playing an increasing part in the detection of gut pathology in paediatric patients. At our hospital, when plain abdominal radiography does not provide a diagnosis, ultrasound is commonly requested to rule out conditions that require urgent attention, such as intussusception, appendicitis and midgut malrotation and volvulus. After these conditions have been excluded however, the ultrasound examination can frequently lead to the diagnosis of several other conditions, including gastroenteritis, Crohn s disease, mesenteric lymphadenopathy and less commonly, duplication cysts, bezoas, and haemolytic uraemic syndrome. Although plain radiography of the abdomen may be suggestive of gut pathology, the additional information provided by sonography often provides a specific diagnosis, leading to better patient care. This paper is a presentation of ten case studies demonstrating the use of ultrasound to augment plain X-ray findings, in order to obtain a final diagnosis. Division of Medical Imaging Women s and Children s Hospital 72 King William Road North Adelaide South Australia 5006 Telephone: Fax: piottol@mail.wch.sa.gov.au INTRODUCTION For a long time now ultrasound has been used as the first examination for suspected hypertrophic pyloric stenosis. Yet there is still a widespread notion that ultrasound does not have a major diagnostic role in evaluating other gut pathology, a role traditionally undertaken by plain x-rays. The signs and symptoms of abdominal pathology are very non-specific. These include colicky abdominal pain, vomiting, diarrhoea, palpable abdominal mass, focal or generalised tenderness, blood and mucus per rectum and fever. Patients with abdominal pathology may present with one or more of these signs and symptoms, making a specific clinical diagnosis very difficult. By far the most common investigation for abdominal pain is the plain radiograph. These are often unhelpful, being normal in as many as one third of cases (unpublished data over a two year period from WCH). They may, however, show evidence of a soft tissue mass or small bowel obstruction. Both of these radiographic signs, although suggestive of the presence of intussusception or ileus, are non-specific. Ultrasound is valuable in the further assessment of these patients, and also in patients whose plain films are normal. The most common gut conditions encountered are appendicitis, intussusception and gastroenteritis. Less common conditions that can be diagnosed with ultrasound include mesenteric lymphadenopathy, midgut malrotation (with or without an associated volvulus) and Crohn s disease. Rarely, conditions such as duplication cysts, haemolytic uraemic syndrome, Henoch Schonlein Purpura, bezoars and malignancies are diagnosed from the ultrasound examination. INTUSSUSCEPTION Intussusception is one of the most common causes of abdominal emergency in early childhood. 1,2,3 In this condition, a segment of the bowel wall invaginates the lumen of the segment immediately distal to it. Intussusception occurs most commonly in the first two years of life, but is occasionally seen in older children and adults, associated with other conditions such as cystic fibrosis. It is thought that most cases arise as a result of hyperplasia of Peyer s patches, the lymphoid tissue of the intestinal wall. The resultant swelling of the intestinal wall is pushed distally by peristalsis, dragging the wall of the bowel with it, together with its attached mesentery. Compromise of venous drainage then results in marked oedema of the involved bowel wall. The commonest location is at the ileocaecal junction, where the ileum invaginates the large bowel this is termed an ileo-colic intussusception. Most commonly, the head of the intussusception is found in the ascending or transverse colon. In advanced cases however, the invagination can extend as far as the sigmoid colon, almost to the anus. The main clinical features are intermittent attacks of colic with drawing up of the legs and the passage of blood and mucus per rectum. These patients often appear very flat. A sausage shaped tumour may be palpable in the abdomen. Later, there may be vomiting due to intestinal obstruction. A review of patients with confirmed ileo-colic intussusception at our institution showed the plain radiographs were normal in 33 per cent of cases. In 57 per cent of cases, a soft tissue mass was apparent, while 19 per cent showed features of small bowel obstruction. On ultrasound examination, all intussusceptions display a concentric ring or doughnut sign, with marked oedema of the bowel wall. The diameter of the intussusception is typically 2.5cm or more. The Radiographer vol. 51, no. 1, April

2 3668 Radiographer Text 1/4/04 2:57 PM Page 12 SONOGRAPHIC APPEARANCES OF COMMON GUT PATHOLOGY IN PAEDIATRIC PATIENTS: COMPARISON WITH PLAIN ABDOMINAL RADIOGRAPHY Case 1 This six-month-old boy presented with intermittent vomiting. His supine abdominal radiograph showed a normal gas pattern throughout, with no evidence of a soft tissue mass (Figure 1a). Due to the clinical presentation of bilious vomiting, further investigation with a barium meal was performed to exclude a proximal small bowel obstruction. The barium study was normal. The subsequent ultrasound examination showed a well defined, rounded mass in the left iliac fossa (Figure 1b), with the concentric ring sign consistent with an ileo-colic intussusception. The intussusception was thought to be at the junction of the descending and sigmoid colons, subsequently confirmed with a barium enema. Figure 1a (far right): Normal supine abdominal radiograph in 6-month old male. Figure 1b (right): Transverse ultrasound image from the left iliac fossa, showing an intussusception, with arrow heads indicating the outer margin of the invaginated bowel. Case 2 A two-and-a-half-year-old boy with intermittent colicky abdominal pain for two days, associated with non-bilious vomiting. Plain radiography showed a rounded soft tissue mass to the right of the midline, possibly representing an intussusception. The bowel gas pattern was non-specific, with no suggestion of obstruction (Figure 2a). The ultrasound examination confirmed the presence of an intussusception in the ascending colon, corresponding to the position of the soft tissue mass seen in the radiograph (Figure 2b). Figure 2a (far right): Supine abdominal radiograph, showing a soft tissue mass (arrow heads) to the right of the midline. Figure 2b (right): Transverse ultrasound image over the soft tissue mass seen on the radiograph, showing an intussusception in the ascending colon. Case 3 This three-year-old boy presented with colicky abdominal pain and bilious vomiting. The abdominal radiograph demonstrated numerous fluid levels within moderately distended bowel loops, extending down to the pelvis. The appearances suggest a distal small bowel obstruction (Figure 3a). The ultrasound study revealed an ileocolic intussusception in the transverse colon (Figure 3b) and confirmed the presence of multiple dilated fluid-filled loops of small bowel, consistent with obstruction. A moderate amount of free fluid was also demonstrated in the peritoneal cavity. Several lymph nodes and some echogenic mesentery were visible within the intussusception. Figure 3b (right): Transverse ultrasound image of the transverse colon, showing an ileo-colic intussusception. The invaginating ileum and its associated mesentery are indicated by arrows, within the colon (arrow heads). 12 The Radiographer vol. 51, no. 1, April 2004

3 3668 Radiographer Text 1/4/04 2:57 PM Page 13 L. PIOTTO AND R. GENT Case 4 Not all intussusceptions are ileo-colic. Transient ileo-ileal intussusception is a common finding in abdominal sonography of paediatric patients, most often seen to the left of the midline. These are rarely symptomatic and resolve spontaneously. They do not cause any significant vascular compromise and therefore do not result in oedema of the bowel wall. Occasionally, two or even three separate segments of ileoileal intussusception may be present simultaneously. The sonographic appearance of an ileo-ileal intussusception is that of a localised expansion of a part of the ileum, with a concentric ring sign (Figure 4) corresponding to the invagination of the bowel. The diameter of these is invariably much less than that of an ileo-colic intussusception. Figure 4 (left): Transverse ultrasound image of an ileo-ileal intussusception (arrow heads) in the left flank of a 3-year old child. Figure 3a (above): Supine abdominal radiograph, showing multiple distended bowel loops. APPENDICITIS Appendicitis is another common abdominal emergency in childhood, and the most common condition requiring emergency surgery. 4 It is thought that most cases result from obstruction of the lumen of the appendix by faecal impaction or a faecolith, which then results in bacterial infection within the obstructed segment. In some cases, the appendix ruptures, resulting in a peri-appendiceal abscess easily demonstrable on ultrasound images. Clinically, patients with appendicitis have focal (rebound) tenderness over the appendix, with associated fever and leukocytosis. An inflamed appendix typically has a diameter of 6mm or more, is non-compressible, blind ending, hyperaemic and may be fluid-filled. When present, an appendicolith appears as a focus of increased echogenicity, not necessarily casting an acoustic shadow. The inflammatory reaction often results in increased echogenicity of the adjacent meso-appendix and omentum. It is also not uncommon to see a small amount of free fluid adjacent to the caecal pole. An inflamed appendix is more difficult to detect with ultrasound when in a retrocaecal position and when it is deep within the pelvis. Ultrasound is frequently useful when the clinical findings do not strongly support appendicitis. This can occur when the appendix is in a relatively high position, near the tip of the liver, or when there is negligible tenderness because the appendix is wrapped in a cushion of oedematous omentum. It is useful to initially concentrate on the region of maximum tenderness. Case 5 This 13-year-old boy presented with onset of severe right sided abdominal pain especially in the right flank. On his abdominal radiograph, apart from a prominent loop of small bowel in the right iliac fossa the radiographic appearances are non specific but raise the possibility of a localised ileus (Figure 5a). Suspicious of appendicitis, an ultrasound examination was performed which revealed a relatively long and swollen retrocaecal appendix (Figure 5b). The thick walled appendix also demonstrated noncompressibility, rather causing indentation of the posterior psoas when pressure was applied from the transducer (Figure 5c). Figure 5a (above): Supine abdominal radiograph suggestive of a localised ileus in the right iliac fossa. Figure 5b (left): Longitudinal ultrasound image in the right iliac fossa, showing a distended and inflamed appendix (arrow heads), lying anterior to the psoas muscle. The Radiographer vol. 51, no. 1, April

4 3668 Radiographer Text 1/4/04 2:57 PM Page 14 SONOGRAPHIC APPEARANCES OF COMMON GUT PATHOLOGY IN PAEDIATRIC PATIENTS: COMPARISON WITH PLAIN ABDOMINAL RADIOGRAPHY Figure 5c (left): Transverse ultrasound image of the inflamed appendix (arrow heads). With transducer pressure applied, the appendix is seen to be non-compressible as it indents the margin of the underlying psoas muscle (arrows). Figure 6a (below right): Supine abdominal radiograph showing a suspected calculus (arrow head) projected over the right edge of the lower sacrum. Figure 6b (below): Oblique pelvic radiograph demonstrating the calculus (arrows). Case 6 A nine-year-old boy with a two week history of fever and right iliac fossa pain was thought to have appendicitis. The A-P abdominal radiograph demonstrated a calcific density projected over the right edge of the lower sacrum (Figure 6a), but which was projected clear of the sacrum in the oblique view (Figure 6b). This was assumed to be an appendicolith. The A-P view showed a normal bowel gas pattern, with a mild scoliosis concave to the right. An ultrasound examination revealed a fluid collection in the pelvis behind the bladder, anterior to the rectum, and containing a small echogenic structure, likely to be the density visible on the radiographs (Figure 6c). The infected nature of the collection is apparent from the reactive oedema of the adjacent posterior bladder wall (Figure 6d). More superiorly was an inflammatory mass of bowel that showed hyperaemia on power Doppler images. A separate appendix could not be identified. MALROTATION Another condition that can present with these symptoms is malrotation of the intestine, resulting from failure of the gut to undergo its normal 270º anticlockwise rotation in the first trimester. Malrotation causes shortening of the root of the mesentery, predisposing the jejunum and ileum to twist around the narrow base. The twisting is referred to as a volvulus (of the midgut), and is a surgical emergency. The signs and symptoms of malrotation include bilious vomiting, abdominal pain and failure to thrive. Case 7 A two-day-old (38 week gestation) twin, vomiting, with large stomach residue and absence of bowel sounds was thought to have an intussusception. A supine radiograph revealed dilated bowel loops, most marked in the left upper quadrant. Bowel gas pattern in the right lower quadrant was normal, but showed some separation of the loops. In the clinical setting, meconium inspissation was thought Figure 6c (above left): Transverse ultrasound image showing a fluid collection (arrow heads) posterior to a distended bladder and containing a calculus (arrow). Figure 6d (above): Longitudinal ultrasound image showing an inflammatory mass of bowel, superior to the hypoechoic collection, with localised thickening (arrow heads) of the posterior bladder wall. The calculus is again visible within the inferior part of the collection. 14 The Radiographer vol. 51, no. 1, April 2004

5 3668 Radiographer Text 1/4/04 4:21 PM Page 15 L. PIOTTO AND R. GENT to be a possibility (Figure 7a). An ultrasound examination showed no intussusception, but did reveal reversal of the normal arrangement of the superior mesenteric vessels, with the SMV positioned on the patient s left of the SMA (Figure 7b). This is indicative of a midgut malrotation. Further scanning revealed the ultrasonic whirlpool sign, pathognomonic of a volvulus. 5 The whirlpool sign is elicited by moving the transducer cranially and caudally while scanning in the transverse plane. This movement demonstrates a corkscrew arrangement of the mesenteric vessels which simulates a whirlpool as the transducer is moved back and forth. A barium meal confirmed the ultrasonic diagnosis of midgut malrotation with associated volvulus. Figure 7a (far right): Supine abdominal radiograph showing some dilated bowel loops in the left upper quadrant. Figure 7b (right): Transverse ultrasound image in the mid abdomen showing reversal of the normal superior mesenteric artery/vein relationship. The artery (long arrow) is seen to lie to the patient s left of the vein (short arrow), anterior to the abdominal aorta (arrow heads). GASTROENTERITIS Patients with gastroenteritis, of viral or bacterial origin, may present with abdominal pain, bilious vomiting and diarrhoea. Ultrasound is not normally used to diagnose gastroenteritis. However, findings consistent with this condition are often found when the examination is being done to exclude the conditions that require intervention. Features of gastroenteritis on ultrasound images include multiple fluid-filled small bowel loops, often with slightly thickened walls and hyperperistalsis. Frequently, a fluid-distended colon is also apparent. Case 8 An 18-month-old girl presented with severe attacks of colic, thought to be due to intussusception. The erect abdominal radiograph demonstrated several air-fluid levels in the right iliac fossa, possibly representing a localised ileus due to an inflammatory process (Figure 8a). An abdominal ultrasound confirmed the presence of multiple fluid-filled loops of small bowel (Figure 8b), together with a distended and fluid-filled colon. In the absence of any other findings, these features are consistent with a diagnosis of gastroenteritis Figure 8a: Erect abdominal radiograph showing several air-fluid levels. Figure 8b: Longitudinal image of the right flank showing multiple fluid-filled loops of small bowel, consistent with gastroenteritis. CROHN S DISEASE Crohn s Disease is the most common inflammatory disease of the bowel, usually affecting the terminal ileum and proximal colon. Clinically, Crohn s disease affects children over the age of ten years, who may present with abdominal pain, diarrhoea, fever and weight loss. The disease appears as symmetrically thickened (greater than 5mm), hypoechoic, hypoperistaltic bowel wall. 6 Inflammatory bowel masses may also be seen in children with this condition, resulting in the formation of fistulae. Case 9 A 14-year-old boy with abdominal pain for a two week period. Plain radiography showed multiple prominent loops of small bowel that do not appear particularly dilated, but do demonstrate thickened mucosal folds. (Figure 9a). An ultrasound examination demonstrated thickened loops of bowel in both The Radiographer vol. 51, no. 1, April

6 3668 Radiographer Text 1/4/04 4:21 PM Page 16 SONOGRAPHIC APPEARANCES OF COMMON GUT PATHOLOGY IN PAEDIATRIC PATIENTS: COMPARISON WITH PLAIN ABDOMINAL RADIOGRAPHY iliac fossae, corresponding to areas of ileal wall thickening, subsequently proven to be due to Crohn s disease (Figure 9b). Figure 9a: Supine abdominal radiograph showing small bowel loops with thickened mucosal folds. Figure 9b: Transverse image of a loop of ileum, which has a thickened wall (outlined by arrow heads) due to Crohn s disease. MESENTERIC ADENITIS Mesenteric lymph node enlargement is commonly seen in patients presenting with acute abdominal pain. The enlarged nodes are most commonly identified in the root of the mesentery and are thought to represent a non-specific finding. 7 This appearance is commonly called mesenteric adenitis. This is essentially a benign condition, although it should be noted that node enlargement can also occur in response to a local inflammatory condition such as appendicitis or neoplastic infiltration. Case 10 A one-year-old boy presented with episodes of grunting and screaming, possibly due to intussusception. There was a normal gas pattern throughout small and large bowel on the plain radiograph. No abnormal loops or soft tissue masses were evident. The prominent gasfilled stomach is non-specific and probably represents swallowed air from crying Figure 10a: Normal supine abdominal radiograph. Figure 10b: Transverse ultrasound image from the mid abdomen, showing prominent lymph nodes (arrow heads). (Figure 10a). Ultrasound examination showed no evidence of an intussusception, but did show several enlarged lymph nodes on the right side, the largest measuring 15mm in length (Figure 10b). In the absence of other findings, the appearances are likely to represent mesenteric adenitis. CONCLUSION Ultrasound is very valuable in the investigation of paediatric patients with acute abdominal pain. With a careful scanning technique, ultrasound can quite often detect a range of gut pathology. Importantly, ultrasound has been very useful in the detection of those conditions that require urgent intervention such as intussusception, appendicitis and malrotation with volvulus. In our hospital, all cases of suspected intussusception have an ultrasound study before any treatment is instituted. In the event that the ultrasound examination does not reveal one of these conditions, it often provides an alternative diagnosis, which can then 16 The Radiographer vol. 51, no. 1, April 2004

7 3668 Radiographer Text 1/4/04 2:57 PM Page 17 L. PIOTTO AND R. GENT allow appropriate treatment. These examinations sometimes require considerable time and patience, particularly if the child is uncooperative or in pain. Analgesia prior to the ultrasound examination is very advantageous. REFERENCES 1. Lim, H.K., Bae, S.H., Seo, G.S., Yoon, G.S. Assessment of reducibility of ileocolic intussusception in children: usefulness of color doppler sonography. Radiology 1994; 191: Woo, S.K., Kim,J.S., Paik, T.W., Choi, S.O. Childhood intussusception: US-guided hydrostatic reduction. Radiology 1992; 182: Shiels, W.E. Editorial Childhood Intussusception: Management Perspectives in J Pediatr Gastroenterol Nutr 1995; 21: Siegel, M.J. 2002, Pediatric Sonography, Lippincott Williams & Wilkins, Philadelphia, USA. 5. Pracros, J.P., Sann, L., Genin, G. et al. Ultrasound diagnosis of midgut volvulus: the whirlpool sign. Pediatr Radiol 1992; 22: Siegel, M.J., Friedland, J.A., Hildebolt, C.F. Bowel Wall Thickening in Children: Differentiation with US. Radiology 1997; 203: Sivit, C.J., Newman, K.D., Chandra, R.S. Visualization of enlarged mesenteric lymph nodes at US examination. Pediatr Radiol 1993; 23: Peer Reviewed Submitted: October 2003 Accepted: February 2004 The Radiographer vol. 51, no. 1, April