IMAGING for ABDOMINAL PAIN

42 y. o. , obese woman with 6 children 42 y.o., obese woman with 6 children. Now has RUQ pain and tenderness, fever, elev. WBC. Pain radiates around to under right scapula

This is a classic history for acute cholecystitis, although ascending cholangitis may present similarly The standard imaging is RUQ ultrasound In abdomen, where is US good, where isn’t it, and why? Enemies of US are gas and bone, which reflect and don’t transmit sound Three “big” areas for US in the “abdomen” are the RUQ, kidneys, and pelvis, because all three can provide a sonographic window without bowel gas in the way (liver displaces bowel out of the RUQ, kidneys can be imaged from the flanks, urinary bladder can be filled to lift bowel out of the pelvis or trans-vaginal and trans-rectal US can get directly to uterus/ovaries and prostate without intervening bowel) Also, US is great for fluid (seeing through GB bile to see stones, seeing dilated bile ducts, determining if renal lesion is cyst or solid, seeing through urinary bladder) Pregnant uterus is perfect for US (sonographic window with uterus displacing bowel, amniotic fluid to transmit sound well, no ionizing radiation)

US findings in acute cholecystitis GB stones Tender GB (sonographic Murphy’s sign) Distended GB Thickened GB wall Pericholecystic fluid Debris/pus in GB lumen Hyperemia on color Doppler Of radiology imaging modalities, US is unique in that it combines simultaneous physical exam with imaging

Following image shows stone in GB Findings diagnostic of GB stone Echogenic focus in GB lumen Acoustical shadowing Mobile (moves with change in position of patient)

HIDA scan is alternative imaging if GB not visible on US Following HIDA scan shown as typical example of nuclear medicine study Uses Technicium 99m What lights up depends on what carrier molecule is attached Compared to other radiology imaging modalities, nuclear studies are only partly about imaging anatomy (the anatomy is typically “fuzzy” on nuclear imaging), but it is also very much about function and physiology (more than other modalities) This HIDA shows serial images of counts obtained at 5-minute intervals, with normal activity entering GB, giving functional information that cystic dust is patent, making acute cholecystitis unlikely

14 y.o girl who initially had crampy, periumbilical pain, that is now more steady and localized to the RLQ. Has focal tenderness in RLQ, mildly increased WBC, and slight fever.

The history suggests acute appendicitis With a classic history and physical for appendicitis, in the hands of an experienced surgeon, no imaging may needed Imaging is otherwise needed, particularly if the history or exam is atypical Plain X-rays would not be indicated because usually appendicitis would be soft tissue/fluid pathology against a normal soft tissue background (no contrast) and would be invisible Following X-ray shows a calcified fecalith (appendicolith) projected just lateral to right SI joint in patient with appendicitis, but this is very insensitive sign, visible on X-ray in fewer than 5% of cases

How much radiation does patient get with abdominal/pelvic CT? Although CT is an excellent imaging exam for appendicitis (95%+ sensitivity and positive predictive value), radiation is an issue, particularly in a young patient How much radiation does patient get with abdominal/pelvic CT? PA CXR gives only about 3-days-worth of radiation that we all get anyway from natural sources Abdominal and pelvic CT may give as much as 100 times radiation of PA CXR What is risk of the radiation from A/P CT? Very little prospective data Worst case guess: Out of 1000 A/P CTs in pediatric patient, may cause one additional cancer in a lifetime Always need to weigh risk versus benefit (CT information may provide very large benefit)

For pediatric patient, as long as radiology dept For pediatric patient, as long as radiology dept. has experience, US is preferred over CT for initial imaging of suspected appendicitis Although its sensitivity is not as good as that of CT when used on all patients, US is effective in smaller pediatric patients, has no radiation, and has a very high positive predictive value

Findings of appendicitis on US Dilated (usually >6mm), non-compressible, tender bowel-like structure in RLQ attached to cecum No peristalsis May see closed end, appendicolith, hyperemia on color Doppler, adjacent inflamed fat or abscess Following image shows abnormal appendix on US in patient with appendicitis

Following images show appendicitis on CT To review a CT, scroll up and down (visually in this case) through images to integrate the slices into a 3-D mental image of one structure at a time (liver, each kidney, colon, etc.) Oral barium has been given in this case, opacifying the ileum making it easier to identify the appendicitis (since its lumen is obstructed and will not fill with contrast) For appendix, find ascending colon in right flank, follow down to tip of cecum, and appendix will be recognized as tubular structure off cecum, but only if one mentally integrates the slices going inferiorly The appendix is dilated, and has “fuzzy fat” around it (inflamed, edematous mesenteric fat)

Following coronal image on patient with appendicitis shows appendicolith in dilated appendix

Multidetector spiral CT rapidly obtains very thin axial slices, allowing acquisition of a volume of data, and subsequent reconstruction of multi-planar images

70 y.o. male with fever, increased WBC, and LLQ pain and tenderness

This is typical history for diverticulitis, most commonly involving the sigmoid colon Plain X-rays not usually helpful because it’s soft tissue/fluid pathology on soft tissue background, although some complications of diverticulitis (free intraperitoneal perforation, obstruction) could be imaged on X-ray US not usually used because there is no good sonographic window, and patients are older

Following CT images show sigmoid diverticulitis Visually scroll through the images to follow the descending colon down to the sigmoid, where the colon wall and mucosal folds are very thickened Also note the “fuzzy fat” around the sigmoid, due to inflammation/edema This case is uncomplicated diverticulitis, without macroscopic abscess, which if of sufficient size would require drainage, usually by interventional radiology

40 y.o. male with intermittent severe right flank pain radiating to groin, and hematuria

The likely diagnosis is a right ureteral stone Because the most common ureteral stone composition is calcium oxalate, they are often visible on plain X-ray (but only about 60% since many stones measure only a few mm, hard to see in a large patient) Therefore X-ray not usually used for initial dx, although helpful for urologic F/U CT is gold-standard imaging study for showing ureteral stones (nearly 100% sensitivity), based on original literature articles from Yale Radiology Dept. But, CT has issue of radiation, particularly in patients who may be young and repeatedly present in ED with stones Current practice trends will include an expanded role for US based on patient history/age and urinalysis

Following 3 CT images show a right UVJ stone causing right hydronephrosis and hydrouereter Study done with “Yale protocol,” using no oral or IV contrast (no oral contrast because not looking for intraperitoneal pathology, no IV contrast since virtually all ureteral stones will be opaque enough to be visible and contrast might actually obscure stone) Stone is at UVJ where most small stones hold up (most stones are small), while large stones hold up at UPJ

80 y. o. male with severe abd. pain, hypotension, and a pulsatile abd 80 y.o. male with severe abd. pain, hypotension, and a pulsatile abd. mass

If patient is stable, not hypotensive, CT is indicated The story suggests a ruptured abdominal aortic aneurysm with a mortality of as much as 50%, so patient needs to go to OR (don’t send unstable patients to radiology) In ED, a quick US could be done, and would usually be able to show an AAA if present, but US unreliable in ruling out the other critical question of rupture/bleed If patient is stable, not hypotensive, CT is indicated No oral contrast is needed: pathology is not intraperitoneal No IV contrast is needed: the 2 key pathologies (AAA, retroperitoneal bleed) are both visible because they are contrasted against retroperitoneal fat If IV contrast were given in this case, the bleed may not light up at all because it is a clot without blood flow; only bleeding that occurred in the 60 sec between contrast injection and scanning would light up

The following 3 CT images show a large ruptured AAA with retroperitoneal bleed Note that this is a completely retroperitoneal bleed because the kidney is displaced, and the descending colon is elevated anteriorly

The following 4 CT images of a trauma case show a lacerated spleen and left kidney, with associated minimal intraperitoneal bleed and large retroperitoneal bleed The case is shown to emphasize the importance of IV contrast administration to show solid organ pathology (blood in splenic lacerations in this case, but also for tumor, e.g.) If IV contrast had not been given in this case, the splenic lacerations may have been hard to see Note that IV contrast does not light up the blood in the lacerations (that’s clotted blood without flow), but it does light up the normally perfused splenic tissue to produce a density difference (contrast)