Acute appendicitis
Updates to Article Attributes
Appendicitis is inflammation of the vermiform appendix. It is a very common condition in general radiology practice and is one of the main reasons for abdominal surgery in young patients. CT is the most sensitive modality to detect appendicitis.
Epidemiology
Acute appendicitis is typically a disease of children and young adults with a peak incidence in the 2nd to 3rd decades of life 1.
Clinical presentation
The classical presentation consists of periumbilical pain (referred) which within a day or later localises to McBurney's point with associated fever, nausea and vomiting 2. This progression is only seen in a minority of cases and is unhelpful in children who often present with vague and non-specific signs and symptoms. It also relies on the appendix being in a 'normal' position, which is not the case in a significant number of cases (see below).
General signs and symptoms include 1-2:
- fever
- localised pain and tenderness
- RLQ pain over appendix (i.e. McBurney
'ssign) - pelvic pain, diarrhoea and tenesmus (pelvic appendix)
- flank pain (retrocaecal appendix)
- groin pain (appendix within an inguinal hernia - Amyand hernia) or a femoral hernia (De Garengeot hernia)
- RLQ pain over appendix (i.e. McBurney
- leucocytosis
- nausea and vomiting
- atypical location: within pelvis (30%),
extra-peritonealextraperitoneal (5%)
The Alvarado score is a clinical score that can be useful to help risk stratify.
Pathology
Appendicitis is typically caused by obstruction of the appendiceal lumen, with resultant build up-up of fluid, secondary infection, venous congestion, ischaemia and necrosis. Obstruction may be caused by 1:
- lymphoid hyperplasia (~60%)
- appendicolith (~33%)
- foreign bodies (~4%)
- Crohn disease or other rare causes, e.g. stricture, tumour, parasite
Radiographic features
One of the biggest challenges of imaging the appendix is finding it. Once confidently identified whether or not it is normal,, assessing its normality is relatively straightforward.
The location of the base of the appendix is relatively constant, located roughly between the ileocaecal valve and the apex of the caecum. This relationship is maintained even when the caecum is mobile.
The location of the tip of the appendix is much more variable, especially as the length of the appendix has an extensive range (2-20 cm) 8. The distribution of positions areis described as 7-8:
- behind the caecum (ascending retrocaecal): 65%
- inferior to the caecum (subcaecal): 31%
- behind the caecum (transverse retrocaecal): 2%
- anterior to the ileum (ascending paracaecal preileal): 1%
- posterior to the ileum (ascending paracaecal retroileal): 0.5%
Plain radiograph
Plain radiography is infrequently able to give the diagnosis, however, is useful for identifying free gas, and may show an appendicolith in 7-15% of cases 1. In the right clinical setting, finding an appendicolith makes the probability of acute appendicitis up to 90%.
If an inflammatory phlegmon is present, displacement of caecal gas with mural thickening may be evident.
Small bowel obstruction pattern with small bowel dilatation and air-fluid levels areis present in ~40% of perforations.
Ultrasound
Ultrasound with its lack of ionising radiation should be the investigation of choice in young patients. With a competent user, ultrasonography is reliable at identifying abnormal appendixes, especially in thin patients. However, the identification of a normal appendix is more problematic, and in many instances, appendicitis cannot be ruled out.
The technique used is known as graded compression, using the linear probe over the site of maximal thickness, with gradual increasing pressure exerted to displace normal overlying bowel gas.
Findings supportive of the diagnosis of appendicitis include 4:
- aperistaltic, noncompressible, dilated appendix ( >6 mm outer diameter)
- appendicolith
- distinct appendiceal wall layers
- echogenic prominent pericaecal and periappendiceal fat
- periappendiceal hyperechoic structure: amorphous hyperechoic structure (usually >10 mm) seen surrounding a noncompressible appendix with a diameter >6 mm 10
- periappendiceal fluid collection
- target appearance (axial section)
- periappendiceal reactive nodal prominence/enlargement
Confirming that the structure visualised is the appendix is clearly essential and requires demonstration of it being blind ending and arising from the base of the caecum. Identifying the terminal ileum confidently is also helpful/
A recently described dynamic ultrasound technique using a sequential 3 step patient positioning protocol has been shown to increase the visualisation rate of the appendix 9. In the study, patients were initially examined in the conventional supine position, followed by the left posterior oblique position (45o LPO) and then a “second-look” supine position. Reported detection rates increased from 30% in the initial supine position to 44% in the LPO position and a further increase to 53% with the “second-look” supine position. Slightly larger absolute and relative visualisation rates were seen in children. The authors suggested that the effect of the LPO positioning step improved the acoustic window by shifting bowel contents.
CT
CT is highly sensitive (94-98%) and specific (up to 97%) for the diagnosis of acute appendicitis and allows for alternative causes of abdominal pain also to be diagnosed. The need for contrast (IV, oral or both) is debatable and varies from institution to institution. Oral contrast has not been shown to increase the sensitivity of CT 11.
CT findings include 1-3:
- dilated appendix with distended lumen ( >6 mm diameter) 3
- thickened and enhancing wall
- thickening of the caecal apex (up to 80%): caecal bar sign, arrowhead sign
- periappendiceal inflammation, including stranding of the adjacent fat and thickening of the lateroconal fascia or mesoappendix
. - extraluminal fluid
- inflammatory phlegmon
- abscess formation
- appendicolith may also be identified
- periappendiceal reactive nodal prominence/enlargement
{{youtube:http://www.youtube.com/watch?v=BI6BgaX6u2k}}
Treatment and prognosis
Treatment is appendicectomy, which can be performed either open or laparoscopically 5. Mortality from simple appendicitis is approximately 0.1% but is as high as 5% in perforation with generalised peritonitis 5.
In ~30% of cases where the appendix has become gangrenous, recovery is complicated by abdominal/pelvic abscess formation. It is in this situation that radiologists have a therapeutic role to play with percutaneous CT- or US guided-guided drainages.
Complications
Recognised complications include 5:
- perforation: in up to 13-30% of cases
- abscess formation: appendiceal abscess
- generalized peritonitis
- pylephlebitis: infective thrombophlebitis of the portal circulation
- complicating hepatic abscess
-
post appendectomy, development ofstump appendicits
Differential diagnosis
Clinically, the most common differential is that of mesenteric adenitis, which can be differentiated by the identification of a normal appendix and enlarged mesenteric lymph nodes.
The imaging differential includes:
- inflammatory bowel disease, especially Crohn disease, which may affect the appendix
- other causes of terminal ileitis
- appendiceal
mucocoelemucocele - lymphoid hyperplasia
- pelvic inflammatory disease (PID)
- right
sided-sided diverticulitis - Meckel
'sdiverticulitis - acute epiploic appendagitis
- omental infarction
- appendiceal malignancy
- enlarged normal appendix as almost
1/250% ofasymptommaticasymptomatic patients can have an appendix diameter greater than 6mm on CT 12
Practical points
on CT, identify first the ileocaecal valve, which usually has lipomatous
wallslips, and then look for the appendix>6 mm outer diameter is a reliable measurement to characterise appendicitis in all imaging modalities
-<p><strong>Appendicitis</strong> is inflammation of the vermiform <a href="/articles/appendix">appendix</a>. It is a very common condition in general radiology practice and is one of the main reasons for abdominal surgery in young patients. CT is the most sensitive modality to detect appendicitis.</p><h4>Epidemiology</h4><p>Acute appendicitis is typically a disease of children and young adults with a peak incidence in the 2<sup>nd </sup>to 3<sup>rd</sup> decades of life <sup>1</sup>.</p><h4>Clinical presentation</h4><p>The classical presentation consists of periumbilical pain (referred) which within a day or later localises to <a href="/articles/mcburneys-point-2">McBurney's point</a> with associated fever, nausea and vomiting <sup>2</sup>. This progression is only seen in a minority of cases and is unhelpful in children who often present with vague and non-specific signs and symptoms. It also relies on the appendix being in a 'normal' position, which is not the case in a significant number of cases (see below).</p><p>General signs and symptoms include <sup>1-2</sup>:</p><ul>- +<p><strong>Appendicitis</strong> is inflammation of the vermiform <a href="/articles/appendix">appendix</a>. It is a very common condition in general radiology practice and is one of the main reasons for abdominal surgery in young patients. CT is the most sensitive modality to detect appendicitis.</p><h4>Epidemiology</h4><p>Acute appendicitis is typically a disease of children and young adults with a peak incidence in the 2<sup>nd </sup>to 3<sup>rd</sup> decades of life <sup>1</sup>.</p><h4>Clinical presentation</h4><p>The classical presentation consists of periumbilical pain (referred) which within a day or later localises to <a href="/articles/mcburneys-point-2">McBurney point</a> with associated fever, nausea and vomiting <sup>2</sup>. This progression is only seen in a minority of cases and is unhelpful in children who often present with vague and non-specific signs and symptoms. It also relies on the appendix being in a 'normal' position, which is not the case in a significant number of cases (see below).</p><p>General signs and symptoms include <sup>1-2</sup>:</p><ul>
-<li>RLQ pain over appendix (i.e. <a href="/articles/mcburney-sign">McBurney's sign</a>)</li>- +<li>RLQ pain over appendix (i.e. <a href="/articles/mcburney-sign">McBurney sign</a>)</li>
-<li>atypical location: within pelvis (30%), extra-peritoneal (5%)</li>-</ul><p>The <a href="/articles/alvarado-score">Alvarado score</a> is a clinical score that can be useful to help risk stratify.</p><h4>Pathology</h4><p>Appendicitis is typically caused by obstruction of the appendiceal lumen, with resultant build up of fluid, secondary infection, venous congestion, ischaemia and necrosis. Obstruction may be caused by <sup>1</sup>:</p><ul>- +<li>atypical location: within pelvis (30%), extraperitoneal (5%)</li>
- +</ul><p>The <a href="/articles/alvarado-score">Alvarado score</a> is a clinical score that can be useful to help risk stratify.</p><h4>Pathology</h4><p>Appendicitis is typically caused by obstruction of the appendiceal lumen, with resultant build-up of fluid, secondary infection, venous congestion, ischaemia and necrosis. Obstruction may be caused by <sup>1</sup>:</p><ul>
-</ul><h4>Radiographic features</h4><p>One of the biggest challenges of imaging the appendix is finding it. Once confidently identified whether or not it is normal, is relatively straightforward.</p><p>The location of the base of the appendix is relatively constant, located roughly between the ileocaecal valve and the apex of the caecum. This relationship is maintained even when the caecum is mobile.</p><p>The location of the tip of the <a href="/articles/appendix">appendix</a> is much more variable, especially as the length of the appendix has an extensive range (2-20 cm)<sup> 8</sup>. The distribution of positions are described as <sup>7-8</sup>:</p><ul>- +</ul><h4>Radiographic features</h4><p>One of the biggest challenges of imaging the appendix is finding it. Once confidently identified, assessing its normality is relatively straightforward.</p><p>The location of the base of the appendix is relatively constant, located roughly between the ileocaecal valve and the apex of the caecum. This relationship is maintained even when the caecum is mobile.</p><p>The location of the tip of the <a href="/articles/appendix">appendix</a> is much more variable, especially as the length of the appendix has an extensive range (2-20 cm)<sup> 8</sup>. The distribution of positions is described as <sup>7-8</sup>:</p><ul>
-</ul><h5>Plain radiograph</h5><p>Plain radiography is infrequently able to give the diagnosis, however, is useful for identifying free gas, and may show an <a href="/articles/appendicolith">appendicolith</a> in 7-15% of cases <sup>1</sup>. In the right clinical setting, finding an appendicolith makes the probability of acute appendicitis up to 90%.</p><p>If an inflammatory phlegmon is present, displacement of caecal gas with mural thickening may be evident.</p><p><a href="/articles/small-bowel-obstruction">Small bowel obstruction</a> pattern with small bowel dilatation and air-fluid levels are present in ~40% of perforations.</p><h5>Ultrasound</h5><p>Ultrasound with its lack of ionising radiation should be the investigation of choice in young patients. With a competent user, ultrasonography is reliable at identifying abnormal appendixes, especially in thin patients. However, the identification of a normal appendix is more problematic, and in many instances, appendicitis cannot be ruled out.</p><p>The technique used is known as <em>graded compression</em>, using the linear probe over the site of maximal thickness, with gradual increasing pressure exerted to displace normal overlying bowel gas.</p><p>Findings supportive of the diagnosis of appendicitis include <sup>4</sup>:</p><ul>- +</ul><h5>Plain radiograph</h5><p>Plain radiography is infrequently able to give the diagnosis, however, is useful for identifying free gas, and may show an <a href="/articles/appendicolith">appendicolith</a> in 7-15% of cases <sup>1</sup>. In the right clinical setting, finding an appendicolith makes the probability of acute appendicitis up to 90%.</p><p>If an inflammatory phlegmon is present, displacement of caecal gas with mural thickening may be evident.</p><p><a href="/articles/small-bowel-obstruction">Small bowel obstruction</a> pattern with small bowel dilatation and air-fluid levels is present in ~40% of perforations.</p><h5>Ultrasound</h5><p>Ultrasound with its lack of ionising radiation should be the investigation of choice in young patients. With a competent user, ultrasonography is reliable at identifying abnormal appendixes, especially in thin patients. However, the identification of a normal appendix is more problematic, and in many instances, appendicitis cannot be ruled out.</p><p>The technique used is known as <em>graded compression</em>, using the linear probe over the site of maximal thickness, with gradual increasing pressure exerted to displace normal overlying bowel gas.</p><p>Findings supportive of the diagnosis of appendicitis include <sup>4</sup>:</p><ul>
-<li>echogenic prominent pericaecal fat</li>- +<li>echogenic prominent pericaecal and periappendiceal fat</li>
-</ul><p>Confirming that the structure visualised is the appendix is clearly essential and requires demonstration of it being blind ending and arising from the base of the caecum.</p><p>A recently described dynamic ultrasound technique using a sequential 3 step patient positioning protocol has been shown to increase the visualisation rate of the appendix <sup>9</sup>. In the study, patients were initially examined in the conventional supine position, followed by the left posterior oblique position (45<sup>o</sup> LPO) and then a “second-look” supine position. Reported detection rates increased from 30% in the initial supine position to 44% in the LPO position and a further increase to 53% with the “second-look” supine position. Slightly larger absolute and relative visualisation rates were seen in children. The authors suggested that the effect of the LPO positioning step improved the acoustic window by shifting bowel contents.</p><h5>CT</h5><p>CT is highly sensitive (94-98%) and specific (up to 97%) for the diagnosis of acute appendicitis and allows for alternative causes of abdominal pain also to be diagnosed. The need for contrast (IV, oral or both) is debatable and varies from institution to institution. Oral contrast has not been shown to increase the sensitivity of CT <sup>11</sup>.</p><p>CT findings include <sup>1-3</sup>:</p><ul>- +<li>periappendiceal reactive nodal prominence/enlargement</li>
- +</ul><p>Confirming that the structure visualised is the appendix is clearly essential and requires demonstration of it being blind ending and arising from the base of the caecum. Identifying the terminal ileum confidently is also helpful/</p><p>A recently described dynamic ultrasound technique using a sequential 3 step patient positioning protocol has been shown to increase the visualisation rate of the appendix <sup>9</sup>. In the study, patients were initially examined in the conventional supine position, followed by the left posterior oblique position (45<sup>o</sup> LPO) and then a “second-look” supine position. Reported detection rates increased from 30% in the initial supine position to 44% in the LPO position and a further increase to 53% with the “second-look” supine position. Slightly larger absolute and relative visualisation rates were seen in children. The authors suggested that the effect of the LPO positioning step improved the acoustic window by shifting bowel contents.</p><h5>CT</h5><p>CT is highly sensitive (94-98%) and specific (up to 97%) for the diagnosis of acute appendicitis and allows for alternative causes of abdominal pain also to be diagnosed. The need for contrast (IV, oral or both) is debatable and varies from institution to institution. Oral contrast has not been shown to increase the sensitivity of CT <sup>11</sup>.</p><p>CT findings include <sup>1-3</sup>:</p><ul>
-<li>periappendiceal inflammation, including stranding of the adjacent fat and thickening of the lateroconal fascia or mesoappendix.</li>- +<li>periappendiceal inflammation, including stranding of the adjacent fat and thickening of the lateroconal fascia or mesoappendix</li>
-</ul><p>{{youtube:http://www.youtube.com/watch?v=BI6BgaX6u2k}}</p><h4>Treatment and prognosis</h4><p>Treatment is appendicectomy, which can be performed either open or laparoscopically <sup>5</sup>. Mortality from simple appendicitis is approximately 0.1% but is as high as 5% in perforation with generalised peritonitis <sup>5</sup>.</p><p>In ~30% of cases where the appendix has become gangrenous, recovery is complicated by abdominal/pelvic abscess formation. It is in this situation that radiologists have a therapeutic role to play with percutaneous CT or US guided drainages.</p><h5>Complications</h5><p>Recognised complications include <sup>5</sup>:</p><ul>- +<li>periappendiceal reactive nodal prominence/enlargement</li>
- +</ul><p>{{youtube:http://www.youtube.com/watch?v=BI6BgaX6u2k}}</p><h4>Treatment and prognosis</h4><p>Treatment is appendicectomy, which can be performed either open or laparoscopically <sup>5</sup>. Mortality from simple appendicitis is approximately 0.1% but is as high as 5% in perforation with generalised peritonitis <sup>5</sup>.</p><p>In ~30% of cases where the appendix has become gangrenous, recovery is complicated by abdominal/pelvic abscess formation. It is in this situation that radiologists have a therapeutic role to play with percutaneous CT- or US-guided drainages.</p><h5>Complications</h5><p>Recognised complications include <sup>5</sup>:</p><ul>
-<li>post appendectomy, development of <a title="Stump appendicitis" href="/articles/stump-appendicitis">stump appendicits</a>-</li>-<li><a href="/articles/appendiceal-mucocele-1">appendiceal mucocoele</a></li>- +<li><a href="/articles/appendiceal-mucocele-1">appendiceal mucocele</a></li>
-<li>right sided <a href="/articles/diverticulitis">diverticulitis</a>- +<li>right-sided <a href="/articles/diverticulitis">diverticulitis</a>
-<li><a href="/articles/meckel-diverticulitis-1">Meckel's diverticulitis</a></li>- +<li><a href="/articles/meckel-diverticulitis-1">Meckel diverticulitis</a></li>
-<li>enlarged normal appendix as almost 1/2 of asymptommatic patients can have an appendix diameter greater than 6mm on CT <sup>12</sup>- +<li>enlarged normal appendix as almost 50% of asymptomatic patients can have an appendix diameter greater than 6mm on CT <sup>12</sup>
-<li><p>on CT, identify first the ileocaecal valve, which usually has lipomatous walls, and then look for the appendix</p></li>- +<li><p>on CT, identify first the ileocaecal valve, which usually has lipomatous lips, and then look for the appendix</p></li>
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