Ultrasound of Acute Appendicitis

Ultrasound of Acute Appendicitis

 Ultrasound imaging of acute appendicitis pearls and pitfalls acute appendicitis is a common abdominal emergency

with a lifetime prevalence of about 

seven percent of the clinical diagnosis of acute appendicitis is a challenge to emergency physicians and surgeons classic symptoms of acute appendicitis are well described however up to one-third of patients with acute appendicitis have atypical presentations.

Ultrasound should be the first line 

imaging modality for diagnosis of acute appendicitis

As it has excellent specificity both in 

the pediatric and adult patients the symptoms of acute appendicitis are frequently non-specific and overlap with various other diseases acute appendicitis occurs at any age but usually, between 10 and 30 years the cause of acute appendicitis is unknown but there are probably many contributing factors the primary cause is probably luminal obstruction which may result from fecalith foreign bodies parasites and primary neoplasms or metastasis these are for cases of suspected acute appendicitis on the image on upper right side of the screen.

 The appendix measuring about

nine millimeters in diameter

it has a very thick hypoechoic wall

on the image on the upper left side of the

screen.

The appendix is distended measuring 

about eight millimeters in diameter it has normal wall thickness and shows

echogenic material within its lumen 

the third case here the appendix measuring about nine millimeters in diameter it shows normal wall thickness with the fluid-filled lumen in the last case here the appendix measuring about 10 millimeters in diameter it shows the normal wall with its lumen is filled with echogenic material which of these is actually acute appendicitis the answer is none of them you will know the reason why these cases are not acute appendicitis.

Ultrasound is the first imaging study of 

choice in acute appendicitis graded compression technique is used with the high-frequency linear probe you take images in transverse and longitudinal planes and you can from the iliac crest to the bladder when you are going to do the examination ask the patient where is the site of maximum tenderness and have them point with one finger because self-localization helps to find the appendix easily don't give up too soon search where the pain is indicated and also search systematically try to find the ileocecal valve and from the ileocecal valve go down for two or three centimeters and usually, that is the location of the appendix

compress the ilium and cecum to look

behind it in retro sequel appendicitis move the probe to the flank and look behind the cecum or try to push the appendix towards the probe by placing the other hand in the flank and pushing the interior in deep pelvic appendicitis in women you can use endovaginal ultrasound to make sure that the appendix is entirely visualized including the blind-ending tip because if you had tip appendicitis you will miss it

if you didn't visualize the entire appendix the

 the appendix is long and thin and it is filled with faces and bacteria

it has a narrow lumen that easily 

obstructs the normal appendix has a mean length of eight to ten millimeters and mean thickness of about four millimeters on ultrasound it has gut signature it has mucosa submucosa muscularis propria and lymphoid tissue and it even has its own mesentery which can be visualized especially when it's inflamed it is located in the right lower abdominal quadrant at McBurney point there are some variations it can be in the left upper abdomen when there is a male rotation it can be retrocecal and it can be in the inguinal canal let's have a look how the appendix looks like on ultrasound this is the gut signature you will find it in any part of the digestive tract and also the appendix there are alternating layers of white and black from the center the white layer is the interface between the mucosal layers then this blackish layer is the mucosa then the white layer is the submucosa then the black layer is the muscular layer and the outer white layer is the serosa

as we can see the same layers are seen 

in the ilium.

what is the important difference between 

the ilium and appendix

The appendix does not show inner folds 

of the mucosa, while the ilium shows folds and why the mucosa is thick in the appendix because of the lymphoid tissue there is a lot of lymphoid tissue in the mucosa of the appendix which is shown as physiological thickening of the mucosa so the normal sonographic appearance of the appendix is that it has inner hypoechoic mucosa without folding its diameter is less than six millimeters and it is compressible sometimes it contains air sometimes stool and there is normal mesenteric fat surrounding it when the lumen of the appendix is obstructed the appendiceal mucosa keeps on secreting mucus causing dilatation of the lumen which obviously has consequences for its vascular supply the intraluminal pressure exceeds the arterial pressure in the appendix wall with subsequent ischemia and necrosis of the wall and further perforation and this is the sequence of events in acute appendicitis luminal obstruction high intraluminal pressure ischemia and necrosis perforation and inflammatory response.

Ultrasound features of acute 

appendicitis we see non-compressible blind-ending tube greater than six millimeters in diameter it is fluid-filled when it's non-perforated the submucosal lining is intact you may see in appendicolith and you can see peri-appendiceal fluid this is a case of acute appendicitis as you can see this is a blind-ending tubular bowel structure that arises from the cecum this is the echogenic submucosa if you see that intact the appendix is likely non-perforated you can see a pentacle which is the echogenic focus with shadowing is seen in about 65 of cases it has the specificity of about 87 for acute appendicitis one important thing to note that if you see pentacles within inflamed appendix there is a higher risk of perforation how to measure the appendix always measure the appendix from the outer border of a muscular layer to the other side outer border of

muscular layer 

in the literature the cut off point is six millimeters this is not reliable because you may

have the appendix normally distended 

with air or fluid with no secondary signs of inflammation and the patient is asymptomatic also in children the appendix can be large due to lymphoid hyperplasia the appendix may be small less than six millimeters but the surrounding tissues showing secondary signs of appendicitis so appendicitis is very unlikely if the diameter is less than six millimeters and six millimeters threshold is highly sensitive but not highly specific the causes of false-negative diagnoses include tip appendicitis an aberrant location of the appendix

such as a retro cycle position 

and perforation in tip appendicitis the inflammation is localized to the

the distal end of the appendix 

the proximal appendix being normal this pitfall can be minimized by imaging

the entire length of the appendix 

as you can see in this case of acute appendicitis the appendix is coming off the cecum the proximal part of the appendix looks good the inflammation starts in the tip of the appendix looking at the tip it appears dilated about eight-millimeter with increased echogenicity of the surrounding fat

so you should visualize the entire 

appendix a retro cycle appendix can be difficult to visualize particularly if the ascending colon and distal small bowel contain large amounts of air that cannot be easily compressed in retro sequel appendicitis move the probe to the flank and look behind the cecum or try to push the appendix towards the probe by placing the other hand in the flank and pushing anterior the majority of appendices are intraperitoneal medial to the psoas muscle but some of them will be retrocecal seen in the paracolic gutter lateral to the psoas muscle here is a case of retrocecal appendicitis