[{"uniqueid":"A1514743326965","title1":"I'm Hungry: Decision Making at 3am","title2":null,"description1":"A multi center review of food choices at 3am","votecount":"2","type":"approved"},{"uniqueid":"A1501777578103","title1":"The Four Quadrants: Acute Pathology in the Abdomen and Current Imaging Guidelines","title2":null,"description1":"Abdominal pain is the most common presenting complaint in emergency departments in the United States[27]<\/span> and can be difficult to evaluate because the physical exam is often misleading and \u201ctextbook\u201d presentations do not occur as often as one might expect. Symptoms can vary widely, and while many patients presenting with severe abdominal pain may prove to have gastroenteritis after an extensive workup, it is often unavoidable because a surgical abdomen can present with seemingly benign symptoms. This article summarizes the most common causes of abdominal pain and the most appropriate imaging studies for evaluation of abdominal pain according to ACR appropriateness criteria.

Right Upper Quadrant:<\/b>

Acute right upper quadrant pain is common complaint that typically prompts a workup of the hepatobiliary system. The differential diagnosis for acute right upper quadrant pain includes acute cholecystitis, bile duct obstruction, cholangitis, acute pancreatitis, acute hepatitis, hepatic abscess or tumor, hepatic laceration in the setting of trauma, disorders of the gastrointestinal tract, pleuro-abdominal pain due to pneumonia or pulmonary infarction, and disorders of the right kidney.

Acute cholecystitis is the primary diagnostic concern in the setting of acute right upper quadrant pain because it can be life-threatening and prompt diagnosis of acute cholecystitis is essential for proper treatment. The clinical history, physical exam, and routine laboratory tests have not yielded acceptable sensitivities and specificities to predict the presence or absence of acute cholecystitis,[63]<\/span> therefore, imaging studies play an important role in the evaluation of right upper quadrant pain.

The current ACR appropriateness criteria for right upper quadrant pain[4]<\/span> includes four variants:

Variant 1: Fever, elevated white blood cell count, positive Murphy sign
Variant 2: Suspected acalculous cholecystitis
Variant 3: No fever, normal white blood cell count
Variant 4: No fever, normal white blood cell count, ultrasound showing only gallstones
Variant 5: Hospitalized patient with fever, elevated white blood cell count, positive Murphy sign
Variant 6: Fever, elevated white blood cell count, pregnant woman

In variants 1, 2, 3, 5, and 6 ultrasound of the abdomen is considered the most appropriate initial imaging study with scores of 9, 8, 9, 9, and 9 respectively (rating scale: 1, 2, 3 usually not appropriate; 4, 5, 6 may be appropriate; 7, 8, 9 usually appropriate). In variant 4, after ultrasound has been performed and demonstrates only gallstones, CT abdomen with IV contrast is considered the most appropriate study with a score of 7 (usually appropriate).

Although cholescintigraphy is known to have a higher sensitivity (97% on cholescintigraphy versus 88% on ultrasound) and specificity (90% on cholescintigraphy versus 80% on ultrasound) for acute cholecystitis,[60]<\/span> ultrasound remains the most appropriate initial imaging test for patients with suspected acute cholecystitis for several reasons including lack of ionizing radiation, short duration of study, greater availability, identification of gallstones or bile duct dilation, and evaluation for alternative diagnoses.[10]<\/span>[28]<\/span> Cholescintigraphy has an ACR appropriateness score of 6 (may be appropriate) in all 4 variants and usually should be performed following an equivocal ultrasound. The most sensitive ultrasound finding in acute cholecystitis is the presence of gallstones in combination with a positive sonographic Murphy sign, but it should be noted that the sonographic Murphy sign has a relatively low specificity for acute cholecystitis and its absence is a unreliable as a negative predictor if the patient received pain medication prior to the study.[15]<\/span> Gallbladder wall thickening (>3 mm) and pericholecystic fluid are secondary findings along with other less specific findings including gallbladder distension and sludge.

If the findings for acute cholecystitis are equivocal based on ultrasound and\/or scintigraphy, CT of the abdomen with IV contrast is usually the most appropriate study to confirm or exclude a diagnosis of acute cholecystitis and to evaluate for complications such as perforation, abscess, gangrene, gas formation, and intraluminal hemorrhage.[62]<\/span> If ultrasound and\/or scintigraphy are negative for acute cholecystitis, CT abdomen with IV contrast is again the preferred exam to evaluate for an alternative diagnosis. The role of MRI in evaluation of acute cholecystitis is not as well studied as CT, but the sensitivity and specificity for MRI are estimated to be 85% and 81% respectively, whereas both the sensitivity and specificity on CT are estimated to be greater than 95%.[37]<\/span> In pregnant patients, MRI is the preferred test to evaluate for acute cholecystitis following an inconclusive ultrasound because it does not expose the patient or fetus to ionizing radiation and can help to diagnose other causes of abdominal pain.[50]<\/span> Additionally, MRCP can be helpful to evaluate for an impacted stone in the cystic duct or common bile duct and prevent unnecessary ERCP by excluding a biliary abnormality.[49]<\/span> Intravenous gadolinium contrast is a class III agent in pregnancy and is not typically administered.

Acute acalculous cholecystitis is more difficult to diagnose with imaging than calculous acute cholecystitis. Acute acalculous cholecystitis is a life-threatening condition that predominantly affects critically ill patients with significant comorbidities. Ultrasound of the abdomen is the most appropriate initial imaging study for suspected acute acalculous cholecystitis with an ACR appropriateness score of 8 (usually appropriate), but the usefulness of ultrasound is limited because gallbladder abnormalities are commonly detected in critically ill patients which do not correlate to clinical or laboratory findings associated with acute acalculous cholecystitis.[13]<\/span> Similarly, CT often demonstrates nonspecific gallbladder abnormalities in critically ill patients limiting its usefulness in acute acalculous cholecystitis.[11]<\/span> Cholescintigraphy is usually performed after an equivocal ultrasound, and is a more sensitive test because most cases of acute acalculous cholecystitis are associated with cystic duct obstruction. False-negative studies have been reported in cases of acute cholecystitis without cystic duct obstruction.[70]<\/span>

In the setting of blunt abdominal trauma or penetrating injury to the abdomen, the liver is one of the most frequently damaged organs. Liver injury is associated with a mortality rate of 8% and is estimated to occur in 5-10% of cases of blunt abdominal trauma.[69]<\/span> Patients can present with right upper quadrant pain, right shoulder pain (from diaphragmatic irritation), hypotension, and shock. Approximately 80% of liver injuries are minor (grades I to III) with lacerations being the most common.[54]<\/span> Other liver injuries include subcapsular or intraparenchymal hematoma, active hemorrhage, major hepatic vein injury, bile duct injury, and arteriovenous fistula. If the patient is hemodynamically stable and does not require immediate surgical exploration, CT with IV contrast is the preferred study for evaluation of liver trauma. CT is 95% sensitive and 99% specific for detecting liver injuries.[5]<\/span> Complications are reported in approximately 20% of cases of non-operatively treated liver trauma and include bile peritonitis or biloma secondary to bile duct injury, delayed hemorrhage, abscess, and acute acalculous cholecystitis. If a bile leak is suspected, a radionuclide study with technetium-99m iminodiacetic acid (HIDA) is the study of choice.[67]<\/span> MRI does not have a significant role in the acute trauma setting but can be used to monitor liver injury and MRCP may be used for the diagnosis and follow-up of bile duct injuries.

In the absence of trauma, and if there is low clinical suspicion for acute cholecystitis or it has been excluded based on imaging findings, other causes of right upper quadrant pain include acute pancreatitis, acute hepatitis, hepatic abscess or tumor, disorders of the gastrointestinal tract, pleuro-abdominal pain due to pneumonia or pulmonary infarction, and disorders of the right kidney.

Right Lower Quadrant:<\/b>

Right lower quadrant pain is responsible for a large number of emergency department visits and is one of the most challenging clinical presentations with a broad differential including life-threatening conditions that may require emergent surgery. The differential diagnosis for acute right lower quadrant pain includes appendicitis, inflammatory bowel disease, infectious or neutropenic colitis, ischemic colitis, right colonic and cecal diverticulitis, ileal and Meckel diverticulitis, appendiceal diverticulitis, malignancy, lymphoma of the ileum or colon, epiploic appendagitis, omental infarction, mesenteric adenitis, endometriosis, intussusception, foreign body ingestion, cecal volvulus, and gynecologic pathologies.

Acute appendicitis is the most common cause of acute right lower quadrant pain requiring surgery and is the primary diagnostic concern in patients presenting with right lower quadrant pain. Imaging may not be necessary in a few patients with acute appendicitis if the clinical presentation and prediction scores (Alvarado score) are sufficiently diagnostic to allow surgery, but the accuracy of prediction scores and clinical exam findings is inferior to imaging and usually insufficient to predict the presence or absence of acute appendicitis.[66]<\/span>[7]<\/span>

The current ACR appropriateness criteria for right lower quadrant pain with suspected appendicitis[3]<\/span> includes four variants:

Variant 1: Fever, elevated white blood cell count, and classic clinical presentation for appendicitis in adults
Variant 2: Fever, elevated white blood cell count, possible appendicitis, atypical presentation, adults and adolescents
Variant 3: Fever, elevated white blood cell count, pregnant woman
Variant 4: Fever, elevated white blood cell count, possible appendicitis, atypical presentation in children (younger than age 14)

In variants 1 and 2, CT of the abdomen and pelvis with IV contrast is the most appropriate initial imaging study with a score of 8 (usually appropriate). In variants 3 and 4, ultrasound of the abdomen is the most appropriate initial study with a score of 8, mainly because the use of ionizing radiation should be avoided whenever possible in pregnant and pediatric patients.

Computed tomography (CT) with IV contrast is the most accurate imaging study for predicting the presence or absence of appendicitis with a sensitivity of 91% and a specificity of 90%. For comparison, ultrasound has a sensitivity of 78% and a specificity of 83%.[64]<\/span> CT results have been shown to be more consistent than ultrasound across all institutions, likely because ultrasound requires greater dependence on operator skill.[19]<\/span> The clinical diagnosis of right lower pain in women of childbearing age is less accurate compared with adult men and there is usually a lower threshold for imaging in this population because several gynecologic pathologies can present as right lower quadrant pain.[55]<\/span> The clinical diagnosis of right lower quadrant pain is also less accurate in elderly patients, and CT is usually the initial study of choice in this population because of its high accuracy in detecting complications of acute appendicitis which occur more frequently in elderly patients.[52]<\/span> The use of MRI for the evaluation of acute appendicitis in the general population has not been well studied, and although MRI may be desirable due to its lack of ionizing radiation, it has limitations including greater cost, lesser availability, and longer acquisition time. The sensitivity and specificity of MRI for the diagnosis of acute appendicitis in adults are estimated to be 85-100% and 95-99% respectively.[9]<\/span>[20]<\/span>[31]<\/span>

Pediatric patients have several unique factors which include increased sensitivity to ionizing radiation, smaller body size, and less body fat which favors initial use of ultrasound. The use of CT and ultrasound for suspected acute appendicitis in pediatric patients is not as well studied relative to adult patients, however, the sensitivity and specificity on ultrasound are estimated to be 88% and 94%, respectively, compared to 94% sensitivity and 95% specificity on CT.[23]<\/span> If ultrasound findings are equivocal, further evaluation with CT is usually recommended. If CT is performed, IV contrast is recommended, but enteric contrast has not been shown to increase sensitivity in children.[36]<\/span> MRI is also an option for evaluating suspected acute appendicitis in pediatric patients with a sensitivity of 98% and and a specificity of 97% (without sedation or IV contrast),[46]<\/span> but MRI has not gained widespread use due to issues of availability, cost, and potential need for sedation.

The use of ionizing radiation should be avoided whenever possible during pregnancy, and ultrasound is the initial imaging test of choice for pregnant patients with suspected acute appendicitis. Findings are often inconclusive on ultrasound, however, and the largest case series available has shown that detection of a normal appendix in pregnant patients by ultrasound is only 2% (compared to 87% on MRI).[51]<\/span> MRI is the preferred test after an inconclusive ultrasound and studies have shown that MRI has comparable sensitivity and specificity to CT without exposing the fetus to ionizing radiation. The sensitivity and specificity of MRI after ultrasound are estimated to be 91% and 99%, respectively, with the appendix visualized in 92% of cases.[12]<\/span>

If there is low clinical suspicion for acute appendicitis or it has been excluded based on imaging findings, other causes of right lower quadrant pain include inflammatory bowel disease, infectious or neutropenic colitis, ischemic colitis, right colonic and cecal diverticulitis, ileal and Meckel diverticulitis, appendiceal diverticulitis, malignancy, lymphoma of the ileum or colon, epiploic appendagitis, omental infarction, mesenteric adenitis, endometriosis, intussusception, foreign body ingestion, cecal volvulus, and gynecologic pathologies. Gynecologic pathologies are typically best evaluated with pelvic ultrasound and according to the ACR appropriateness criteria for acute pelvic pain in the reproductive age group,[1]<\/span> pelvic ultrasound has an appropriateness score of 9 (usually appropriate), followed by contrast-enhanced pelvic MRI with a score of 6 (may be appropriate) and contrast-enhanced pelvic CT with a score of 4 (may be appropriate).

Left Upper Quadrant:<\/b>

Left upper quadrant pain is often nonspecific and is not associated with a classic primary diagnostic concern such as acute cholecystitis in the right upper quadrant, acute appendicitis in the right lower quadrant, and diverticulitis in the left lower quadrant. There are currently no ACR appropriateness criteria for evaluation of left upper quadrant pain. Left upper quadrant pain can originate from the chest, abdomen, or diaphragm and the differential includes cardiac pain, pneumonia or pleurisy, aortic aneurysm or dissection, splenomegaly, ruptured spleen as a result of trauma, splenic infarction or malignancy, gastric ulcer, gastritis, gastric carcinoma, nephroureterolithiasis, pyelonephritis, left colon and splenic flexure diverticulitis, infectious or inflammatory colitis, colonic malignancy, constipation, pancreatitis, pancreatic tumors, peritonitis, subphrenic or pericolic abscess, localized musculoskeletal pain, referred pain from spinal pathology, and medical causes such as diabetic ketoacidosis or Henoch-Schonlein purpura.

In the setting of blunt chest or abdominal trauma with associated left upper quadrant pain, a focused assessment with sonography for trauma (FAST) scan is usually performed in the emergency department at the time of presentation. It is invariably performed by a clinician who should be formally trained and is intended to aid rapid decision making. The major aim of a FAST scan is to identify intra-abdominal free fluid which is assumed to be hemoperitoneum in the context of trauma. FAST scan has a reported sensitivity of 90% and specificity of 95% for detecting intraperitoneal free fluid, but its sensitivity for detecting solid organ injuries is much lower and absence of free fluid does not rule out solid organ injury.[16]<\/span> After FAST scan and in a hemodynamically stable patient that does not require emergent surgery, CT of the chest, abdomen, and pelvis with IV contrast is the next most useful imaging study to evaluate for complications of trauma such as fractures, lung contusion, diaphragmatic injury, solid organ injury, bowel perforation, and intra- or extra-peritoneal hemorrhage.

Contrast-enhanced CT is the modality of choice for assessing splenic trauma. Splenic parenchyma should be assessed in the portal venous phase because heterogeneous contrast enhancement on the arterial phase can mimic splenic laceration or contusion. It should be noted, however, that the arterial phase combined with the delayed phase is useful for differentiating active hemorrhage from pseudoaneurysms and AV fistulas.[42]<\/span>[14]<\/span> Splenic lacerations are most often graded according to the American Association for the Surgery of Trauma (AAST) splenic injury scale. Complications of splenic trauma include delayed rupture, pseudocysts, splenic abscess, and splenic artery pseudoaneurysm.[29]<\/span> Traumatic left renal injury can also produce left upper quadrant and\/or left flank pain. The AAST renal injury scale is the currently the most widely used system for grading renal contusion, laceration, subcapsular perinephric hematoma, vascular injury, and collecting system injury.[45]<\/span>

For patients presenting without a history of trauma, the most appropriate imaging modality will depend largely on the clinical history and physical exam. Splenomegaly can be associated with left upper quadrant pain, and causes of an enlarged spleen include infection (most commonly infectious mononucleosis), hematologic disease, metabolic\/storage disease, malignancy, and connective tissue disorders. Ultrasound is the preferred imaging modality to evaluate for splenomegaly which should be correlated with age-adjusted normograms, with the maximum normal dimension of the spleen in an adult is 13 cm. Splenic infarction is also associated with left upper quadrant pain (~33%) and tenderness (~35%), but patients can be asymptomatic (~40%) or present with constitutional symptoms such as fever and chills or diffuse abdominal pain.[58]<\/span> The majority of splenic infarcts are either due to hematologic disorders (e.g. sickle cell disease) or embolic events (e.g. infectious endocarditis, atrial fibrillation).[48]<\/span> Although splenic infarcts can be seen on ultrasound and are typically hypoechoic compared to the normal splenic parenchyma, CT is often considered the imaging study of choice because ultrasound is less specific and acute infarcts tend to be isoechoic to normal spleen parenchyma. Contrast-enhanced CT should be performed in the delayed phase to avoid heterogeneous enhancement. Hyperacute infarcts may be seen as areas of mottled increased attenuation representing areas of hemorrhagic infarction. The classic appearance of an infarct on CT is a peripheral, wedge-shaped region of decreased attenuation.[58]<\/span>[53]<\/span>

Disorders of the left kidney can present as left upper quadrant and\/or left flank pain. Acute pyelonephritis occurs most commonly in sexually active young females as a result of retrograde passage of bacteria from the bladder, through the ureter, and into the upper urinary tract.[25]<\/span> The most common organism is E. coli (~90%).[35]<\/span> Symptoms are variable but include left flank and left abdominal pain\/tenderness, fever, dysuria, urgency, nausea, vomiting, and diarrhea.[21]<\/span> Ultrasound is insensitive to changes of acute pyelonephritis and abnormalities are identified in only ~25% of cases. Ultrasound findings in acute pyelonephritis include particulate matter or debris in the collecting system, reduced areas of cortical vascularity on power Doppler, gas bubbles, and focal areas of decreased echogenicity in the renal parenchyma.[21]<\/span> CT is a more sensitive modality for evaluation of the renal tract and can assess for renal calculi, gas, perfusion defects, obstruction, and collections. A single 45-90 second post-contrast CT scan is usually sufficient to diagnose acute pyelonephritis, but if renal colic is suspected a non-contrast scan should be performed first to assess for renal calculi.[21]<\/span> On contrast-enhanced CT, acute pyelonephritis will appear as one or more focal wedge-like areas of hypoenhancement compared to the normal renal parenchyma. The periphery of the cortex is also affected with acute pyelonephritis which helps to differentiate pyelonephritis from a renal infarct which tends to spare the periphery. MRI is usually reserved for patients who are pregnant, and findings in acute pyelonephritis are similar to those seen on CT with affected regions appearing hypointense on T1, hyperintense on T2, and demonstrating hypoenhancement on T1 postcontrast images.[41]<\/span> An infected renal cyst or infected necrotic mass may produce symptoms that are similar to pyelonephritis, and a prior CT or MRI demonstrating a cyst or mass in the same location can be helpful to differentiate these pathologies. In rare cases renal cell carcinoma may cause pain, but the classic triad of macroscopic hematuria, flank pain, and a palpable flank mass are only found in 10-15% of patients and usually indicates advanced disease.[24]<\/span> More commonly, renal cell carcinoma is diagnosed with CT or MRI for the assessment of hematuria or as an incidental finding. Almost half of all renal cell carcinomas are found incidentally on imaging performed for other purposes.[24]<\/span>

Acute pancreatitis usually causes upper abdominal pain radiating to the mid back with associated symptoms of fever, vomiting, tachycardia, and leukocytosis.[44]<\/span> Alcohol abuse and bile duct obstruction are the two most common causes of acute pancreatitis, with 20% of cases being idiopathic.[33]<\/span> The diagnosis of acute pancreatitis is made by fulfilling two of the following three criteria: (1) acute onset of persistent severe epigastric pain, (2) lipase\/amylase elevation >3 times the upper limit of normal, (3) characteristic imaging features on contrast-enhanced CT, MRI, or ultrasound.[8]<\/span> Arterial and portal venous phase CT provides the most most comprehensive initial assessment for acute pancreatitis, but it should be noted that imaging studies may be normal in mild cases. Typical findings on CT include focal or diffuse parenchymal enlargement, changes in density resulting from edema, indistinct pancreatic margins due to inflammation, and surrounding retroperitoneal fat stranding. A lack of parenchymal enhancement indicates liquefactive necrosis and gas may be present if the necrotic tissue becomes infected. Abscess formation and hemorrhage are other complications of acute pancreatitis. Contrast-enhanced MRI is equivalent to CT in the evaluation of pancreatitis but is more expensive and less widely available. The main role of ultrasound is to identify gallstones as a possible cause of pancreatitis and diagnose vascular complications such as thrombosis. The revised Atlanta classification is an international multidisciplinary classification of acute pancreatitis severity, and factors include local and systemic determinants of severity, discrimination of early (1st week) and late (>1 week) clinical phases of pancreatitis, and radiographic findings to distinguish between interstitial edematous pancreatitis and necrotizing pancreatitis.[8]<\/span>

There are several other potentially life-threatening processes which can present as left upper quadrant pain but generally produce less specific symptoms including myocardial infarction, aortic aneurysm or dissection, gastric ulcer, gastric carcinoma, subphrenic or pericolic abscess, colonic malignancy, pancreatic tumors, peritonitis, pneumonia, and referred pain from spinal pathology.

Left Lower Quadrant:<\/b>

The most common cause of left lower quadrant pain in adults is acute descending and\/or sigmoid colon diverticulitis and it is estimated that up to 25% of patients with diverticulosis will eventually develop diverticulitis.[18]<\/span> The differential for left lower quadrant pain includes diverticulitis, constipation, incarcerated hernia, infectious or inflammatory colitis, ischemic bowel, omental infarct, urinary tract infection, ureterolithiasis, prostatitis, ectopic pregnancy, endometriosis, ruptured ovarian cyst, ovarian torsion, malignancy, pelvic congestion syndrome, uterine fibroids, vasculitis, dissection or aneurysm, abscess, abdominal wall hematoma, and retroperitoneal hemorrhage.

Acute diverticulitis should be suspected in patients with the clinical triad of left lower quadrant pain, fever, and leukocytosis. The cause of diverticulitis is thought to be mechanical. The presence of stagnant nonsterile fecal material within a diverticulum compromises blood supply to the thin walled sac, which increases susceptibility to invasion by colonic bacteria causing inflammatory erosion of the mucosal lining and perforation. The severity ranges from mild to severe and complications such as peritonitis and abscess or fistula formation can result from perforation.[57]<\/span> Mild diverticulitis can be treated medically, but severe diverticulitis may require emergent surgery as a result of complications.

The current ACR appropriateness criteria for left lower quadrant pain with suspected diverticulitis[2]<\/span> includes only one variant:

Variant 1: Typical clinical presentation for diverticulitis, suspected complications, or atypical presentations

The recommended initial imaging test is CT abdomen and pelvis with IV and oral contrast with an appropriateness score of 9 (usually appropriate). CT abdomen and pelvis without IV contrast has a score of 6 (may be appropriate) and should be considered when alternate diagnoses are high on the differential, such as ureterolithiasis.

CT is the imaging exam of choice for evaluating patients with suspected descending or sigmoid colon diverticulitis because it has high sensitivity and specificity and can exclude other causes of left lower quadrant pain that mimic diverticulitis.[22]<\/span>[43]<\/span> CT is also useful for planning percutaneous intervention from complications of diverticulitis such as perforation or abscess. One prospective study reported that CT has a sensitivity of 100% and a specificity of 91% for detecting a contained perforation, and a sensitivity of 100% and specificity of 97% for detecting abscess formation.[68]<\/span> When an abscess is present, CT-guided or ultrasound-guided percutaneous drainage of the abscess may help to avoid multiple surgical procedures or in some cases completely eliminate the need for surgery.[26]<\/span> In the past, contrast enema was the primary imaging study for diverticulitis but has been replaced by CT because it does not demonstrate extraluminal abnormalities such as pericolonic inflammation or abscesses.[38]<\/span> In certain circumstances, contrast enema may still be helpful as a follow-up study if there is a suspected fistula or for surgical planning after treatment.[47]<\/span>

Pelvic ultrasound should be strongly considered as the initial imaging exam in women of childbearing age that present with acute left lower quadrant pain since gynecologic processes such as ovarian torsion, ectopic pregnancy, and pelvic inflammatory disease can mimic diverticulitis. If ultrasound is equivocal or fails to identify a cause of left lower quadrant pain, CT is the most appropriate next imaging modality in a nonpregnant patient.[34]<\/span>[65]<\/span> A few studies have reported that graded-compression sonography can be used to evaluate for diverticulitis, with a sensitivity of 77%-98% and a specificity of 80%-99%, but ultrasound requires greater dependence on operator skill than CT and generally has less reproducible results across different institutions.[39]<\/span>[30]<\/span> Additionally, sonography is much more dependent on body habitus than CT or MRI.

The role of MRI in the setting of left lower quadrant pain is not as well studied as CT, but the available studies report that diverticulitis can be detected on MRI with a sensitivity of 86-94% and specificity of 88-92%.[6]<\/span>[17]<\/span>[59]<\/span> MRI is comparable to CT for evaluating for complications of diverticulitis, although it can be more difficult to detect extraluminal gas on MRI.[32]<\/span> Although MRI may be eventually become feasible as the initial imaging exam for suspected diverticulitis, MRI has not gained widespread use due to issues of availability and cost. MRI has a potential role for imaging younger patients with recurrent episodes of diverticulitis to reduce radiation exposure. In pregnant women presenting with left lower quadrant pain, MRI is considered the next best imaging modality after pelvic ultrasound since the use of ionizing radiation should be prevented whenever possible during pregnancy.

The major limitation of CT is the potential difficulty in differentiating diverticulitis from colon carcinoma. The presence of pathologically enlarged lymph nodes (1 cm or greater) in the pericolonic mesentery may increase suspicion for colon cancer. Studies have also shown that there is increased likelihood of colon cancer when abscess, perforation, or fistula is identified.[40]<\/span> If there is no pericolonic lymphadenopathy, edema at the root of the sigmoid mesentery, and inflammatory change near a thickened segment of colon, diverticulitis is favored.[61]<\/span> Follow-up colonoscopy after a CT diagnosis of acute descending or sigmoid diverticulosis is not routinely recommended, but if findings are suspicious for colon cancer or the patient has not had age-appropriate colon cancer screening, colonoscopy is the preferred study.[56]<\/span>

Plain radiographs usually do not show any findings in uncomplicated diverticulitis, but a partial bowel obstruction may occasionally be seen. Pneumoperitoneum, portal venous gas, and extraluminal air-fluid levels may be noted on plain radiographs in patients with complicated diverticulitis. Nuclear medicine imaging has no role in the evaluation of left lower quadrant pain.

If there is low clinical suspicion for acute descending and sigmoid colon diverticulitis or it has been excluded based on imaging findings, other causes of left lower quadrant pain include inflammatory bowel disease, infectious or neutropenic colitis, ischemic colitis, right colonic and cecal diverticulitis, ileal and Meckel diverticulitis, appendiceal diverticulitis, malignancy, lymphoma of the ileum or colon, epiploic appendagitis, omental infarction, mesenteric adenitis, endometriosis, intussusception, foreign body ingestion, cecal volvulus, and gynecologic pathologies.

Conclusion:<\/b>

With several different imaging options available and considering that the history and physical exam can often be misleading, it\u2019s not surprising that healthcare providers are unsure which imaging study is most appropriate for evaluating patients who present to the emergency department with abdominal pain. The American College of Radiology currently has appropriateness criteria for patients presenting with right upper, right lower, and left lower quadrant pain and there are different variants for each of these quadrants depending on patient demographics, physical exam findings, and laboratory data. Left upper quadrant pain is not associated with a classic primary diagnostic concern such as acute cholecystitis in the right upper quadrant, acute appendicitis in the right lower quadrant, and acute diverticulitis in the left lower quadrant, therefore, there are currently no ACR appropriateness criteria for evaluation of left upper quadrant pain. Clinicians should be aware of the ACR appropriateness criteria and, whenever possible, should be using the criteria as a guide to help them order the most appropriate imaging study.
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