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Student Corner: CT Evaluation of Appendicitis

April 9, 2015

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Appendicitis is commonly encountered in the ER and is the leading cause of surgical emergency in the abdomen. The initial evaluation for a presentation that is concerning for appendicitis often includes history taking and exam, supplemented by labs. The Alvarado Score is a 10 point rating scale that is widely used as a tool to help decide whether or not a patient presenting with abdominal pain requires CT imaging (although it’s overall clinical usefulness is controversial). It is outlined here by MDCalc. According to the rule, a score of greater than 4 warrants CT evaluation and greater than 7 requires immediate surgical consult.  CT scan is a highly sensitive and specific tool in diagnosing appendicitis, however it comes with radiation, cost, and sometimes IV contrast risks.  In the pediatric patient population radiation from CT scans are not as desirable as the long-term consequences have theoretical potential to be deleterious (long discussion…for another post maybe!).

The purpose of this article is to go over characteristics of appendicitis that can be seen on a CT scan. The use of contrast is a long debated point of contention amongst the emergency medicine community and the usual practice varies between institutions. Medscape has a great rundown of the issue here, which notes that the use of contrast may be more beneficial in circumstances where appendicitis is a relatively less likely diagnosis because the contrast better helps characterize other possibilities.  Contrast studies are also more helpful in the patient not expected to have a large amount of intraperitoneal fat.

As usual, it is important to understand the local anatomy when analyzing radiological images of the abdomen. The image below is an example of an axial cut, non-contrast abdominal CT of a patient who came in with abdominal pain concerning for appendicitis. Try to identify the following structures: vertebrae, psoas major, IVC, iliac arteries, small bowel, colon and appendix.

Appy

And below is a labeled version of the same image:

Appendicitis labeled

Key: Blue arrow = bowel gas, ascending colon; Green arrows = small bowel; Purple arrows = L and R Iliac arteries; Yellow arrow = IVC; Red arrow = inflamed appendix

This image contains several signs that indicate that the appendix is inflamed. They include:

  • Diameter greater than 6mm–this usually implies the the appendix has either been twisted or blocked off from the cecum by an appendicolith, which causes inflammation
  • Periappendiceal fat stranding–seen as distinct lines that radiate out from the appendix in the image above, it is caused by inflammation of the appendix causes fluid accumulation around the wall of the appendix which turns the normally hypodense surrounding fat into a hyperdense area; note that the visceral fat around the appendix on the L side of the image looks much different than the visceral fat on the other side of the image
  • Appendiceal wall thickening–normally the wall of the appendix is thin and barely noticeable, but this image shows that the wall is generally thickened and may even be slightly more hyperdense than expected (more below)

Other signs that aid in the diagnosis of appendicitis include:

  • Appendiceal wall enhancement–the wall of the appendix becomes slightly more hyperdense when you compare it to the wall of any other loop of bowel, which is again a product of inflammation; note that this finding is usually more evident on contrast-enhanced CT
  • Abscess–the colon has a large reservoir of commensal bacteria, which can grow and wall off into an abscess if they are trapped in the appendix
  • Appendicolith–a calcified mass that is hyperdense on CT which can be an obstruction between the cecum and the appendix

Overall, CT has a high degree of sensitivity and specificity when used to evaluate the possibility of appendicitis. The clues outlined above, especially when seen together and as a part of a larger clinical picture that fits with appendicitis, are instrumental in confirming the diagnosis.

References:

Ohle R, O’Reilly F, O’Brien KK, Fahey T, Dimitrov BD. The Alvarado score for predicting acute appendicitis: a systematic review.BMC Med. 2011 Dec 28;9:139. doi: 10.1186/1741-7015-9-139. Review. PubMed PMID: 22204638; PubMed Central PMCID: PMC3299622.

Reich B, Zalut T, Weiner SG. An international evaluation of ultrasound vs. computed tomography in the diagnosis of appendicitis.Int J Emerg Med. 2011 Oct 29;4:68. doi: 10.1186/1865-1380-4-68. PubMed PMID: 22035447; PubMed Central PMCID: PMC3215954.

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Flank Pain…

February 10, 2015

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Flank pain for several days, history of nephrolithiasis:

Flank Pain 1 Flank Pain 2 Flank Pain 3 Flank Pain 4

This patient has marked right hydronephrosis with significant right renal perinephric inflammatory cystic changes extending into the contiguous right psoas musculature and right retroperitoneum. There is perinephric stranding and edema.

The differential in this case includes renal abscess (most likely) with extension into the right psoas and retroperitoneum.  Additional considerations are atypical infection such as tuberculosis, and urothelial malignancy.

The patient ended up having Xanthogranulomatous pyelonephritis.  This is a subacute/chronic pyelonephritis usually incited by a staghorn calculus.  For more information on this entity please see radiopaedia.org:

http://radiopaedia.org/articles/xanthogranulomatous-pyelonephritis

Author:  Russell Jones, MD

References

1.  Knipe H, Gaillard F et al.  Xanthogranulomatous Pyelonephritis.  www.radeopaedia.org.  Accessed 1/2015.

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Massive splenomegaly…Answer

November 17, 2014

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Last week I showed you this CT showing massive splenomegaly:

Splenomegally + Masses

 

The abdominal CT above shows massive splenomegaly with various areas of hypo attenuation throughout the spleen.  Massive splenomegaly is a term used when the volume of the spleen is expected or calculated to be >1000 grams or clinically extends well into the left lower quadrant or past midline.

A short differential diagnosis for massive splenomegaly includes (1):

  • Malaria
  • Myelofibrosis
  • Leukemia (especially CML)
  • Polycythemia Vera
  • Lymphoma (several types)
  • Lieshmaniasis
  • Thalessemia

The ill-defined hypo attenuated lesions in this spleen raise a high concern for lymphoma.

Author:  Russell Jones, MD

References

1.  Luo EJ, Levitt L.  Massive Splenomegaly.  Hospital Physician, 5/2008.  Accessed 11/2014 at: http://www.turner-white.com/memberfile.php?PubCode=hp_may08_spelnomegaly.pdf

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Massive splenomegaly…

November 12, 2014

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This patient presented with left upper quadrant abdominal pain:

Splenomegally + Masses

 

The abdominal CT above shows massive splenomegaly with various areas of hypo attenuation throughout the spleen.

In the ED, the spleen is not often the organ responsible for non-traumatic pain in the left upper quadrant.  Gastric, colonic, and kidney disorders are much more predominant.  In this example however the spleen is definitively causing the patient’s discomfort.

What is your differential diagnosis for massive splenomegally?

Answer to follow

Author:  Russell Jones, MD

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Liver mass…differential diagnosis

July 14, 2014

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This patient presented with right upper quadrant pain.  I asked last week what your differential diagnosis would be:

Liver Mass 1

Liver mass 2

The CT above shows a multiloculated, rim-enhancing mass in the liver parenchyma.  This is consistent with an abscess.  The differential diagnosis starts by breaking down the categories into bacterial, fungal, and amebic causes. 

Bacterial:  Abscesses can form from ascending cholangitis, especially in setting of biliary malignancies.   Klebsiella pneumoniae has been reported to cause hepatic abscesses, especially in E. Asia (1).  Patients with recent instrumentation (hepatocellular carcinoma embolization, etc) are at risk for MRSA, streptococcus species.  Tuberculosis has been known to cause hepatic abscesses as well.

Fungal:  Disseminated candidiasis in the immunocompromised host can lead to liver and splenic abscesses

Amebic:   Liver abscess is the most common manifestation of extraintestinal entamoeba histolytica (2).  In endemic areas or travelers to endemic areas are at risk for this occurrance. 

Author:  Russell Jones, MD

References

1.  Davis J, McDonald M.  Pyogenic Liver Abscesses.  www.uptodate.com

2.  Leder K, Weller P.  Extraintestinal Entamoeba Histolytica Amebiasis.  www.uptodate.com

 

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Liver mass…

July 7, 2014

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This patient presented with right upper quadrant pain…

Liver Mass 1

Liver mass 2

The CT above shows a multiloculated, rim-enhancing mass in the liver parenchyma.  What is your differential diagnosis?

Author:  Russell Jones, MD

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More colonic dilitation…

June 9, 2014

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This patient presented with abdominal pain, nausea, vomiting, and distention:

Volvulus 1 Volvulus 2 Cecal Volvulus 2 Cecal Volvulus

These films and CT show colonic dilatation similar to last week (sigmoid volvulus).  However, in contrast to last week, this is a cecal volvulus.  In this CT there is marked dilatation of the cecum with a central location in the abdomen.  Usually a cecal volvulus will have visible haustra as opposed to a sigmoid volvulus in which colonic haustra will not be present.  Sometimes, as in the above images, the haustra are difficult to see.  This also looks like it may be a more rare form of cecal volvulus called a cecal bascule.  For more information I will defer to our radiology colleagues at Radiopaedia:

Caecal Volvulus

For all you radiologists out there, do you think this is consistent with a cecal bascule?

Why note the difference between cecal and sigmoid volvulus?  The treatment can be drastically different.  Sigmoid volvuli are many times amenable to acute management non-operatively (sigmoidoscopy) whereas cecal volvuli usually require open laparotomy and have a higher frequency of partial colectomy.

Author:  Russell Jones, MD

References

1.   Gaillard F et al.  Caecal Volvulus. http://radiopaedia.org/articles/caecal_volvulus

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Colonic dilitation…

June 2, 2014

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This is a 50 year old male who presented with nausea, vomiting, and abdominal distention.  His initial plain film showed:

CV 1

A CT scan was ordered for given suspicion for colonic obstruction:

CV Scout 1 CT Swirl 1

 

The CT scout film clinches the diagnosis with the classic “Coffee Bean” sign consistent with a sigmoid volvulus. The CT scan not only shows the massively dilated colon but demonstrates the associated “swirl” sign of the mesentery (arrow). He underwent a flexible sigmoidoscopy with partial reduction of his volvulus.  He then underwent a colectomy for definitive management of his volvulus.  He had a return of bowel function and discharged a week later.

Author:  John Ray, MD

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Tearing abdominal pain…

April 24, 2014

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This is a 60 year old male who presented with tearing abdominal pain…

SMA dissection 1

This CT angiogram of the abdomen shows a superior mesenteric artery dissection.  The aorta was normal.  On the above CT image you can see a flap dissecting the SMA.

SMA dissection is a rare pathology in the abdomen.  It can lead to localized mesenteric ischemia and presents with severe abdominal pain.  It is treated various ways including medical management and observation, endovascular repair, or surgical revascularization (1).  Many times it is associated with aortic dissection with a dissection flap extending into the SMA.

Image contributor:  James Chenoweth, MD

Author:  Russell Jones, MD

References

1.  Gobble RM, Brill ER, Rockman CB et-al. Endovascular treatment of spontaneous dissections of the superior mesenteric artery. J. Vasc. Surg. 2009;50 (6): 1326-32.

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Abdominal pain…

March 24, 2014

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Patient had RLQ abdominal pain, we obtained a CT looking for appendicitis:

Pill frags 1

The patient has multiple, radiodense objects throught the small bowel.  Upon further history this patient was taking multiple calcium and iron supplement pills a day. 

Author:  Russell Jones, MD

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