Pediatric Radiology

, Volume 43, Issue 2, pp 232–242

Beyond acute appendicitis: imaging of additional pathologies of the pediatric appendix

Authors

  • Kelly R. Dietz
    • Amplatz Children’s Hospital, Department of RadiologyUniversity of Minnesota
    • Department of RadiologyCincinnati Children’s Hospital Medical Center
  • Daniel J. Podberesky
    • Department of RadiologyCincinnati Children’s Hospital Medical Center
  • Alexander J. Towbin
    • Department of RadiologyCincinnati Children’s Hospital Medical Center
Pictorial Essay

DOI: 10.1007/s00247-012-2565-1

Cite this article as:
Dietz, K.R., Merrow, A.C., Podberesky, D.J. et al. Pediatr Radiol (2013) 43: 232. doi:10.1007/s00247-012-2565-1

Abstract

Primary acute appendicitis is by far the most common pathological condition affecting the appendix. There are differential diagnoses, however, when an abnormal appendix is found by imaging. The purpose of this paper is to highlight the imaging and clinical manifestations of less common appendiceal abnormalities in children. Familiarity with these alternative diagnoses might be particularly helpful in guiding management of the child whose clinical presentation is not typical for primary acute appendicitis.

Keywords

AppendixAppendicitisAppendiceal neoplasmCystic fibrosisChildren

Introduction

Primary acute appendicitis, defined as appendiceal inflammation caused by appendiceal obstruction and superimposed bacterial infection, is by far the most common pathology of the appendix. Imaging evaluations to exclude this diagnosis occur daily in the pediatric radiology setting. The clinical and imaging differential diagnosis in a child with right lower quadrant pain and suspected appendicitis is a broad but well-recognized list that predominantly involves structures adjacent to the appendix such as the ovaries, small bowel, large bowel and urinary tract. There are, however, less common pathologies involving the appendix that can create an imaging diagnostic dilemma in the setting of right lower quadrant symptoms. Some of these entities merely mimic appendicitis by imaging or clinical presentation. Others lead to a secondary appendicitis, though the causal relationship between the underlying pathology and the inflammation is often unclear.

Cystic fibrosis and the appendix (Figs. 1 and 2)

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Fig. 1

Cystic fibrosis. Images of an 8-year-old, previously healthy girl with a persistent palpable hard mass in the right lower quadrant for several weeks. a Longitudinal right lower quadrant US with colour Doppler shows a diffusely dilated (9-mm diameter) non-compressible appendix (arrows) medial to the cecum (not shown but containing a stool ball corresponding to the palpable abnormality). The child reported no clinical symptoms of appendicitis and was not tender to compression. b An outside CT of the same child obtained 3 weeks prior to the US then became available for review. Axial contrast-enhanced CT image shows the stool ball (dashed arrow) in the cecum as well as the dilated appendix (arrow) without surrounding inflammation. Fatty infiltration of the pancreas was also noted (not shown here). Based on these findings, sweat chloride testing was recommended and found to be positive for cystic fibrosis

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Fig. 2

Cystic fibrosis. Images of a 3-year-old girl with a history of cystic fibrosis who presented to the emergency department with abdominal pain and decreased appetite. a Longitudinal right lower quadrant US image shows an enlarged, non-compressible appendix (arrow) measuring 8 mm in diameter near its tip. b The base of the appendix measures 10 mm (arrows) and is distended by echogenic material. The girl was tender upon attempted appendiceal compression. Dilated small bowel is seen anteriorly (asterisks in a and b). c Axial contrast-enhanced CT image shows the mildly dilated appendix (arrow) without surrounding fatty edema or free fluid. There are multiple dilated fluid- and stool-containing small-bowel loops (asterisks) consistent with a small-bowel obstruction. The girl improved with conservative therapy for a bowel obstruction and did not require appendectomy

The abnormally thickened luminal contents found in children with cystic fibrosis (CF) can result in chronic distention of an otherwise normal appendix. The majority of asymptomatic CF patients have an appendix ≥ 6 mm in diameter by US (with a mean of 8.3 mm), whereas the generally accepted upper limit of normal in an otherwise healthy child is < 6 mm [1].

Additionally, children with CF have a lower incidence of acute appendicitis compared with the general population(1–2% versus 7%) [2]. It is hypothesized that the inspissated secretions in the appendix actually protect against appendicitis. However, children with cystic fibrosis who develop acute appendicitis are more likely to experience complications such as perforation caused by a delay in diagnosis [2].

Inflammatory bowel disease and the appendix (Figs. 3, 4, 5 and 6)

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Fig. 3

Crohn disease. MR enterography of an 11-year-old previously healthy boy with abdominal pain and chronic diarrhoea. a Coronal fat-suppressed 2-D balanced steady-state free-precession MR enterography shows an enlarged (12-mm diameter) appendix (arrow) without any other bowel abnormalities. b Coronal fat-suppressed post-contrast T1-weighted MR enterography shows the abnormally enlarged and enhancing appendix (arrow) without any other bowel abnormalities. The appendectomy specimen revealed Crohn disease

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Fig. 4

Crohn disease. MR enterography of a 19-year-old man with a history of Crohn disease who presented with right lower quadrant fullness and pain. Coronal fat-saturated contrast-enhanced T1-weighted MR enterography shows a fistula (dashed arrow) from the inflamed appendix (arrow) to the ileum (open arrow)

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Fig. 5

Crohn disease. Image of a 12-year-old boy with a new diagnosis of Crohn disease. Axial contrast-enhanced CT shows wall thickening, mucosal hyperenhancement and surrounding fatty edema of the appendix (arrow), terminal ileum (asterisk) and cecum (open arrow). The appendix is enlarged (22 mm at its base, 7 mm at its tip)

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Fig. 6

Ulcerative colitis in a 13-year-old girl. Axial contrast-enhanced CT shows an enlarged appendix measuring up to 9 mm (arrow) with mucosal hyperenhancement and surrounding fat stranding concerning for appendiceal involvement. However, the adjacent cecum (asterisk) is normal. Wall thickening, mucosal hyperenhancement and adjacent vascular engorgement extend from the rectum to the transverse colon (seen here at the sigmoid and descending colon, open arrow). The girl was treated with anti-inflammatory medications for ulcerative colitis and did not require appendectomy

While uncomplicated primary appendicitis most commonly exhibits isolated appendiceal inflammation without thickening of the adjacent bowel, appendiceal inflammation in the setting of Crohn disease is usually seen with concurrent cecal or terminal ileal involvement. Crohn disease isolated to the appendix, while uncommon, has a favorable prognosis over that affecting the ileum or colon, with recurrence rates of up to 8% [3]. Follow-up of these children is controversial, with some thought that appendectomy might be curative [3].

One of the hallmarks of ulcerative colitis is its continuous involvement of the colon; however, children can have discontinuous involvement (i.e. a “skip lesion”) in the appendix [4].

Hirschsprung disease and the appendix (Fig. 7)

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Fig. 7

Hirschsprung disease and the appendix in a 5-week-old boy with abnormal stooling and abdominal distention. a Water-soluble contrast enema shows a microcolon (dashed arrows) with small bowel dilation (arrows) and a right upper quadrant gas collection (open arrow). In this clinical and radiological setting, a microcolon is most suggestive of total colonic Hirschsprung disease. Biopsies confirmed this diagnosis. b Axial contrast-enhanced CT shows a large gas and fluid collection (arrow) in the right retroperitoneum displacing the right kidney (asterisk) anteriorly. This retroperitoneal abscess was considered to be secondary to a retrocecal appendiceal perforation in the setting of total colonic Hirschsprung disease

Neonatal appendicitis is very rare with high rates of perforation (82.5%) and mortality (28%) [5, 6]. It is most commonly associated with prematurity (possibly resulting from necrotising enterocolitis), inguinalhernias (i.e. the Amyand hernia), cystic fibrosis and Hirschsprung disease [5, 6]. Rectal suction biopsies and placement of a decompressing cecostomy should be considered at the time of appendectomy as long-segment or total-colonic Hirschsprung disease can present as neonatal appendicitis [6].

Amyand hernia (Figs. 8 and 9)

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Fig. 8

Amyand hernia (i.e. an inguinal hernia containing the appendix) in a 19-day-old boy with irreducible lump in the right groin and abdominal distension. a Longitudinal gray-scale US of the right hemiscrotum shows a thickened, tubular structure (arrows) with gut signature adjacent to the testicle (asterisk). b Longitudinal US with colour Doppler shows hyperemia of the testicle (asterisk) adjacent to this thickened tubular structure (arrows) suspected to represent the appendix. Surgery confirmed an Amyand hernia with perforated appendicitis in the scrotum

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Fig. 9

Images from an adult with incidental findings. Double contrast barium enema shows the appendix (arrows) herniated into the right inguinal canal toward the scrotum. A tiny appendiceal diverticulum (open arrow) is present (usually seen in adults > 30 years old)

The Amyand hernia, an inguinal hernia containing the appendix, is very uncommon. The entity is named after Claudius Amyand, the surgeon who reported the first successful appendectomy in 1735 on a boy with appendiceal perforation in an inguinal hernia secondary to an ingested pin [7].

The reported incidence of a normal appendix in an inguinal hernia is 0.5–1.0% [8]. Amyand hernias are most commonly seen on the right side given the usual right lower quadrant location of the appendix. If an Amyand hernia is seen on the left, then situs inversus, intestinal malrotation or a mobile cecum should be considered [8].

Occasionally, the Amyand hernia contains an inflamed appendix (0.1% of inguinal hernia cases) [8]. Preoperative diagnosis of herniated appendicitis can be difficult because of its overlapping presentation with an incarcerated or strangulated inguinal hernia [8].

As noted previously, acute appendicitis is uncommon in neonates and is usually associated with underlying pathology. One review showed that 29 of 111 cases of neonatal appendicitis arose in an inguinal hernia and that this particular subset of neonatal appendicitis cases had an improved prognosis versus other etiologies, likely because of the operative implications of a clinically apparent incarcerated inguinal hernia [9].

Intussusception and the appendix (Figs. 10, 11 and 12)

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Fig. 10

Intussusception of the appendix in a 13-month-old boy with vomiting and abdominal tenderness. Transverse US image shows an ileocolic intussusception (dashed arrows) with a classic target appearance. A tubular structure suggestive of a normal appendix (solid arrow) is seen in the intussusceptum (open arrow). The intussusception was reduced with air enema but recurred multiple times. The boy was ultimately taken to the operating room where an edematous appendix was resected. Pathological review, however, showed no appendiceal inflammation or mass

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Fig. 11

Intussusception in an 18-month-old boy with episodic abdominal pain and vomiting. a Transverse US through the right lower quadrant shows a typical ileocolic intussusception (arrows). This was later reduced by air enema. b Longitudinal US shows a mildly enlarged appendix (arrows) lying outside the intussusception and measuring up to 7 mm in diameter with a small amount of periappendiceal free fluid (asterisk). The appendiceal wall measured up to 2 mm in thickness (with recent literature promoting 1.7 mm as the upper limit for normal [19]). The boy’s symptoms resolved after intussusception reduction without clinical or laboratory findings concerning for acute appendicitis, suggesting that the appendiceal wall thickening was caused by secondary congestion

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Fig. 12

Intussusception of the appendix in a 17-year-old boy with right lower quadrant abdominal pain. Coronal contrast-enhanced CT shows an inflamed appendix (arrow) and surrounding edematous fat (open arrow) inverted into the contrast-filled cecum (asterisk) without ileocolic intussusception. Cecostomy confirmed inversion of an inflamed appendix

Intussusception of the appendix can occur in isolation (e.g., appendiceal inversion or invagination into the cecum, which can be incidental or caused by an appendiceal lesion) or as part of an ileocolic intussusception. The appendix serves as a pathological lead point in approximately 0.2% of all ileocolic intussusception cases [10].

Approximately 25% of isolated appendiceal intussusception (or inversion) cases occur in children, but the appendix is more likely to be inflamed in children with this entity (76%) than in adults (19%) [11].

Of note, it is unclear whether all reported cases of appendicitis found in intussusception truly represent inflammation or infection rather than secondary vascular congestion or edema.

Carcinoid of the appendix (Figs. 13 and 14)

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Fig. 13

Carcinoid of the appendix in a 14-year-old girl with 1 day of right lower quadrant abdominal pain. Longitudinal US from the right lower quadrant shows an enlarged appendix (arrows) measuring 8 mm in diameter with diffuse wall edema, surrounding fat infiltration (dashed arrow) and an echogenic intraluminal focus (open arrow) with posterior acoustic shadowing initially thought to represent a calcified appendicolith. Surgical pathology revealed a carcinoid tumour in the midportion of the inflamed appendix without an appendicolith. Of note, calcification in appendiceal carcinoids, which are frequently less than 10 mm in size, has been reported as a possible appendicolith mimic [23]

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Fig. 14

Carcinoid of the appendix in a 14-year-old boy with 1 week of abdominal pain and rebound tenderness in the right lower quadrant. Axial contrast-enhanced CT shows that the mid-appendix (arrow), which contains oral contrast agent, is thickened and lies along an inflammatory collection (open arrow). The base of the appendix (not shown here) was normal and contrast-filled. The boy was treated with IV antibiotics for 6 weeks for presumed ruptured appendicitis, after which he underwent an appendectomy. Surgical pathology showed a carcinoid tumour of the appendix with ruptured appendicitis

Malignant neoplasms involving the appendix are rare, found in only 0.9–1.4% of appendectomy specimens. Most cases are not diagnosed preoperatively [12]. Carcinoid tumors are by far the most common malignancy of the appendix and much more commonly present with acute appendicitis than with carcinoid syndrome [12].

Laparoscopic resection is considered safe in adults given that appendiceal carcinoids are relatively indolent malignancies overall. This has not been evaluated in children, in whom carcinoid tumors have been found to be more aggressive (because of an increase in serosal and fat involvement) [13]. However, because small carcinoids (the majority of lesions) are unsuspected preoperatively, they are often removed laparoscopically in children as well. In general, appendectomy is considered curative for carcinoid tumors confined to the appendix that are less than 2 cm in size [14].

Mucocele of the appendix (Fig. 15)

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Fig. 15

Mucocele of the appendix in a 16-year-old boy with right lower quadrant pain concerning for appendicitis. US demonstrates an enlarged, non-compressible, fluid-filled appendix (arrow) measuring 9 mm in diameter. Pathological examination revealed a mucocele of the appendix without inflammation

Mucoceles of the appendix are rare, found in only 0.25% of appendectomy specimens [15]. They are more commonly found incidentally (e.g., during elective appendectomy in gynecological cases) than in cases of suspected appendicitis. Mucoceles of the appendix are most common in adults and are rarely seen in adolescents [15].

Mucoceles are described on a benign to malignant histological spectrum from simple mucocele to mucinous cystadenoma to mucinous cystadenocarcinoma. Caution should be taken in performing appendectomies for suspected mucoceles given an elevated risk historically of port-site recurrences and pseudomyxoma peritonei [15].

Lymphoma of the appendix (Fig. 16)

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Fig. 16

Lymphoma of the appendix in a 15-year-old boy with abdominal mass and pain. Axial contrast-enhanced CT shows a large soft-tissue-density mass (arrows) in the right lower quadrant and pelvis that encases vessels and displaces bowel. No discernible appendix is seen. Surgical exploration and pathological examination revealed diffuse appendiceal, cecal and ileal infiltration by Burkitt lymphoma

Appendiceal involvement in non-Hodgkin lymphoma is rare, occurring in 1–3% of all non-Hodgkin patients [16]. Burkitt lymphoma is the most frequent pediatric subtype of non-Hodgkin lymphoma overall (34%) and can occur anywhere, though it is most common in the ileocecal region in children [16]. Nearly all reported pediatric cases of appendiceal lymphoma are caused by the Burkitt subtype [17]. Of note, Burkitt lymphoma is a rapidly growing tumor with the potential to double in size in 24 h [16].

Fecal impaction of the appendix (Figs. 17 and 18)

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Fig. 17

Fecal impaction of the appendix in a 9-year-old boy presenting with fever and right lower quadrant pain. US demonstrates an enlarged appendix (arrows) measuring 8 mm in diameter and filled with echogenic material. However, the appendix was compressible and without adjacent inflammatory change. The boy was cleared clinically by the consulting surgical service without complication

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Fig. 18

Fecal impaction of the appendix in a 5-year-old boy presenting to the emergency department after a motor vehicle accident. Contrast-enhanced CT demonstrates an enlarged appendix (arrows) measuring 8 mm in diameter and filled with fecal material. There is no periappendiceal inflammatory change, and the boy had no signs or symptoms of appendicitis

The appendix can become impacted with non-shadowing fecal material in the normal patient, resulting in enlargement and a diminished compressibility suggestive of appendicitis. The presence of an intact appendiceal wall and lack of surrounding fluid and fat inflammation, in conjunction with the clinical and laboratory findings, can provide reassurance that the appendix is normal [18].

Appendiceal colic

Of note, this appearance may represent the modern imaging equivalent of the appendiceal fecal casts described on barium enemas and, under great controversy, publicized as a finding of “appendiceal colic” by Schisgall [20] in the 1980s. Appendiceal colic is described as recurrent lower abdominal pain in children attributable to contractions of the appendix attempting to expulse hardened fecal material [20, 21]. Though little has been published on appendiceal colic in recent years, the existence of this entity remains debated with some surgical reports of pain relief from appendectomy in this setting [22].

Appendicoliths (Fig. 19)

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Fig. 19

Appendicolith in a 12-year-old boy with intermittent lower abdominal pain over several weeks. a Supine abdominal radiograph shows a 10-mm lobular calcification (arrow) in the right lower quadrant; this finding was unchanged compared with radiographs obtained 2 years earlier. b Longitudinal right lower quadrant US image shows a normal appendix body (arrows). The appendiceal tip is distended by the echogenic appendicolith (dashed arrows), which shows posterior acoustic shadowing. The boy was not tender to compression and showed no periappendiceal inflammatory changes

The significance of a calcified appendicolith in an otherwise normal appendix has been a long-standing source of controversy, mainly in regard to: (1) the unclear association with chronic pain, and (2) the likelihood of ultimately developing appendicitis. Recent literature suggests that children with appendicoliths found in otherwise normal appendices by CT are at no increased risk of developing acute appendicitis [24, 25]. However, a few such cases that have undergone prophylactic appendectomy have shown inflammation on pathological examination. Interestingly, one of these papers reported that 64% of such patients who underwent follow-up imaging without interval appendectomy no longer showed an appendicolith, though the size of those initial appendicoliths was not published [25].

Foreign bodies in the appendix (Fig. 20)

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Fig. 20

Foreign body in the appendix of a 5-year-old girl presenting after swallowing a bracelet. a Abdominal radiograph shows an unchanging tubular configuration of the metallic bracelet (arrow) in the right lower quadrant, suggesting an appendiceal location. b Using intraoperative fluoroscopy, the appendix (arrow) was grasped at its tip (open arrow) to try to manipulate the bracelet fully into the appendix from the cecum. Ultimately, a small cecostomy was required in addition to the appendectomy for complete removal of the bracelet

Almost 95% of swallowed foreign bodies pass through the gastrointestinal tract without incident [26]. A 1971 study showed that 0.0005% of patients developed appendicitis from foreign bodies. This was down from 3% during 1923–1962, likely because of a decreased use of sewing pins and a decreased consumption of wild game hunted with buckshot/birdshot [26]. Colonoscopic removal of appendiceal foreign bodies has been described in adults [26].

Parasites and the appendix (Fig. 21)

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Fig. 21

Parasites and the appendix in a 9-year-old boy presenting with fever and right lower quadrant pain. a Axial contrast-enhanced CT shows a dilated, thick-walled appendix (arrow) with adjacent fat inflammation (dashed arrow) and a small periappendiceal abscess (open arrow) typical of perforated appendicitis. b, c At surgery, a mobile pinworm (open arrows) is seen coursing across the serosal surface of the inflamed, perforated appendix (arrows)

A variety of parasites can be found in the appendiceal lumen, including Enterobius vermicularis (pinworms), Ascaris lumbricoides (roundworms) and Entamoeba histolytica. Pinworms are found in the gastrointestinal tracts of 4–28% of children worldwide with the highest prevalence in 5- to 10-year-olds. Pinworms are found in 0.6–13% of resected appendices (including those without inflammation) [27]. Given that they are not typically invasive, however, the role of pinworms in appendicitis is unclear.

Other appendiceal abnormalities (not shown)

A secondary inflammation of the appendix can occur with other adjacent inflammatory processes such as neutropenic colitis and tubo-ovarian abscess. A recent retrospective study attempting to differentiate tubo-ovarian abscess from acute appendicitis by CT showed an abnormal appendix by imaging in 2% of confirmed tubo-ovarian abscess cases [28].

Appendiceal inflammation has rarely been reported concomitantly with ovarian torsion, though it is not clear from all published reports whether true primary inflammation of the appendix was present histologically rather than secondary to changes of vascular congestion or ischemia. In fact, one case reported twisting of the ovary around the appendix with necrosis of the appendiceal tip [29].

Isolated torsion of the appendix has also been described with and without underlying pathology, most frequently in adults. Fewer than 15 pediatric cases have been reported in the literature, including two infantile cases. One of these was recently reported in an 11-week-old girl with peritoneal signs and a sonographically distended, non-compressible appendix that was found to be torsed and necrotic intraoperatively with gangrenous appendicitis found upon pathological examination [30].

Conclusion

Despite the frequency of primary acute appendicitis, there are differential diagnoses when an abnormal appendix is found by imaging. Familiarity with these alternative diagnoses may be particularly helpful in guiding management of the child whose clinical presentation is not typical for primary acute appendicitis.

Conflicts of interest

The following coauthors have relevant financial relationships or potential conflicts of interest related to the material: A.C. Merrow is an author and content manager for Amirsys Inc.; D.J. Podberesky is on the speaker’s bureau for Toshiba of America Medical Systems; A.J. Towbin is an author for Amirsys Inc.

Copyright information

© Springer-Verlag Berlin Heidelberg 2012