O ver the past 10 years, sonography

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1 Perspective Sonography and the Acute Abdomen: Practical Considerations Julien B. C. M. Puylaert1, Friso M. van der Zant1, Arie M. Rijke2 O ver the past 10 years, sonography.. has gained acceptance for examining patients with acute abdominal pain. Sonography is dynamic, noninvasive, rapid, inexpensive, and readily accessible; however, it has some serious drawbacks. Use is limited in obese patients; the ultrasound beam cannot penetrate bone or gas; and sonography, more than other radiologic techniques, is operator-dependent and requires skill, dedication, and experience. In this perspective, several practical aspects of using sonography on patients with acute abdominal pain are highlighted. These aspects include the choice between sonography and CT as an initial examining technique, the timing of the sonographic examination, sonographically guided puncture, the value of indirect sonographic findings, the significance of normal findings on a sonogram, and, finally, communication with the clinician. Indications Traditionally, surgeons have accepted a high negative laparotomy rate to avoid the risks of ill-advised surgical delay. Nonetheless, serious surgical delay inside the hospital is common. A prospective study of patients with a suspected appendicitis showed a negative laparotomy rate of 27%; and concomitant serious therapeutic delay in 14% of patients who needed surgery [1]. Another prospective study dividing patients into three categories (high, equivocal, and low clinical suspicion) showed that even in the highsuspicion group, 35% of the patients did not have an appendicitis, whereas 5% of the patients in the low-suspicion group had an inflamed appendix [2]. In 30 patients with a ruptured aortic aneurysm, treatment was delayed more than 6 hr because of misdiagnosis [3]. These figures show that the clinical diagnosis of an acute abdomen is unreliable and that the threshold for radiologic imaging studies should be low. The concept of sonography as a helpful diagnostic tool used only in cases of clinical doubt is and should be rejected. The impact of sonography on clinical management of patients with an acute abdomen is impressive. In a study of patients with suspected appendicitis, sonographic findings significantly changed the therapeutic management in 26% of patients [4]. In three independent studies using sonography, negative laparotomy rates were 13%, 13%, and 7%, respectively, [4-61 with a concomitant reduction in unnecessary surgical delay. In our institution, virtually all patients with acute or subacute abdominal pain are referred for a sonogram, including patients for whom surgery seems definitely required as well as patients with a remote possibility ofrequiring surgery (Figs. 1 and 2). Not surprisingly, sonography of the acute abdomen has markedly affected routine practice in many institutions. Sonography performed on indication of acute abdominal pain makes up 25% of all abdominal sonographic examinations at our institution, and nationwide, acute abdominal pain has become the most frequent reason for radiologists to go in to the hospital when they are on call. Sonography or CT as Initial Technique? Several acute abdominal conditions are more easily detected on a CT scan than on a sonogram. They include a ruptured aortic aneurysm, an aortic dissection, an esophageal rupture, a mycotic aneurysm, an acute pancreatitis, an incarcerated internal hernia, and perirenal and hepatic abscesses. In addition, CT scans usually provide better results in obese patients who have retrocecal appendicitis, appendiceal abscess, deeply located sigmoid diverticulitis, closed-loop bowel obstruction, gastrointestinal perforation to the retropetitoneum, and emphysematous cholecystitis. However, in experienced hands, the sonograrn can still be used to reliably diagnose most acute abdominal conditions in most patients [4]. Therefore, a reason- Received June 1, 1995; accepted after revision July 23, Department of Radiology, Westeinde Hospital. Ujnbaan 32, 2512 VA The Hague, the Netherlands. Address correspondence to J. B. C. M. Puylaert 2Department of Radiology. Health Sciences Center, University of Virginia. Lee St, Charlottesville, VA AJR 1997;168: X/97/ American Roentgen Ray Society AJR:168, January

2 Puylaert et al. Fig year-old man with acute appendicitis had 2-day history of constipation and uncomfortable sensation in lower abdomen. No local or rebound tenderness and no fever were present Erythrocyte sedimentation rate was 32 mm! hr with normal leukocyte count Proposed management was conservative. A and B, Sonography showed inflamed appendix in longitudinal (A) and transverse (B) plane. Appendix was subsequently removed. able course of action is to begin with the least expensive and least invasive technique and proceed to a CT scan only in cases of an inconclusive sonogram. Examination Technique Examination of the entire abdomen, from the axilla to the groin. in patients with acute abdominal pain is more than a routine survey of all abdominal organs. The examination involves a sonographically guided. rational approach to the clinical problem of that particular patient. During the examination, the radiologist should continuously consider all possible differential diagnoses depending on the sonographic findings. This symptomdirected sonographic examination requires communication with the patient because specific findings may raise specific questions and. conversely, information provided by the patient may lead to a search for a specific sonographic feature (Fig. 3). Similarly. sonographic examination is closely linked with physical examination. A dual exami- nation is helpful when identifying what organ or structure corresponds to the most painful area or palpable mass. For example. if in women the most tender region is deep in the pelvis, vaginal sonography may help not only in detecting gynecologic conditions but also in diagnosing sigmoid diverticulitis 171or appendicitis [8] (Fig. 4). Asking patients to point out the most tender region can be especially important in conditions that typically cause localized tenderness but do not have conspicuous sonographic features. Segmental omental infarction 19]. epiploic Fig year-old previously healthy man was admitted with classical presentation of acute appendicitis. No diarrhea was present WBC was 16,500!mm3. Immediate appendectomy was proposed. AD, Sonography shows mucosal inflammation ofterminal 1- eum in transverse (A) and longitudinal (B) planes as well as enlarged mesenteric lymph nodes (C). Appendix (arrows) was small and measured 2.1 mm during compression. Surgery was cancelled. Three days later, Salmonella paratyphi B (D) was cultured from stool. a = iliac artery, v = iliac vein. 180 AJR:168, January 1997

3 Sonography and the Acute Abdomen appendagitis f 10), an incarcerated spigelian or epiga.stric hernia, a small rectus hematoma [I I], or sigmoid diverticulitis [ I 2, 13j are a few such conditions (Figs. 5 and 6). On the other hand. diagnostic signs can be found at a considerable distance from the most tender region. In appendicitis. the pain is sometimes diffuse in the lower abdomen, a patient may present with a perforated duodenal ulcer that causes right lower quadrant pain because the gastric contents track down the right parecolic gutter. small-bowel obstruction may cause maximum pain at a marked distance from the site of obstruction (Fig. 7), a stone in the distal ureter may present with only flank pain, air in the biliary system with small bowel obstniction may indicate a gallstone ileus, or liver metastases may indicate an underlying malignancy in patients with an appendiceal mass. These examples all emphasize the importance of examining the entire abdomen. If the anatomy is aberrant. especially in the case of an inflamed appendix far removed from the point where the gridiron incision is normally made. The appendix should be marked on the skin with an indelible pencil (Fig. 8). Sonography in patients with an acute abdomen should be performed with graded compression similar to gentle palpation [ 14). Compression shortens the distance from the transducer to the abnormal structure and allows the use of a high-frequency probe. It is also used to compress or displace gas-containing bowel. thereby reducing the disturbing effect of gas on the sonographic images. Compression also involves determining the extent an organ and its surrounding tissues can be compressed. For instance, compression allows identification of gallbladder hydrops as well as assessment of appendiceal rigidity in appendicitis (Fig. 9). Finally, compression should always be applied in a graded manner to minimize pain. If. despite compression. gas continues to hamper the sonographic examination, the patient can be scanned with the transducer positioned posterolaterally over the flank. In this manner. ventrally located gas in partially Fig year-old woman with 10-year history of abdominal pain complained of recurrent urinary tract infections. A, Sonography showed thickened small-bowel loops (b) with interloop fistula (black arrows). Adjacent bladder wall was locally irregular (white arrows). B, Small amount of air was found in dome of bladder (arrowhead). Only on specific questioning did patient recall episode of urinating air. She was diagnosed with Crohns disease with fistulization to bladder. fluid-filled bowel loops or gas-containing abscesses can be avoided (Fig. 10). With the patient in a left lateral decubitus position, free air should specifically be looked for between the lateral abdominal wall and the liver. Timing of the Sonographic Examination Many acute abdominal conditions show a tendency toward spontaneous resolution; however, symptoms may recur later. Intermittent episodes of abdominal pain are predominantly seen in cases of obstruction. When the obstruction is relieved, the symptoms resolve. and when the obstruction recurs, the symptoms reappear. This scenario is seen in biliary and urinary stone disease. appendicitis. intussusception, incarcerated hernia, and small-bowel obstruction from adhesions. Sonographic findings during an episode of pain may differ significantly Fig year-old woman complained of lower abdominal pain in pelvic region for 1 day. Transabdominal sonography was normal. Transvaginal sonography revealed inflamed appendix (arrow). Fig. 5.-Infarcted epiploic appendix. 40-year-old man had severe pain on pressure in left lower quadrant, suspect for sigmoid diverticulitis. Erythrocyte sedimentation rate was 36 mm!hr. A, At point of maximum tenderness, sonography showed 2.5-cm ovoid area of inflamed fat (arrowheads). B, CT scan confirmed diagnosis of infarcted epiploic appendix (arrowheads). AJR:168, January

4 Puylaert et al. Fig. 6.-Otherwise healthy middle-aged woman presented with severe localized pain in right lower quadrant. She was suspected of having appendicitis. A, Sonography showed small, impalpable rectus hematoma (arrowheads). B, Rectus hematoma (arrowheads) was confirmed by CT scan. Appendectomy was cancelled. Fig. 1.-Incarcerated obturator hernia. 86-year-old woman presented with small-bowel obstruction. A, Left-sided groin sonography revealed small, impalpable herniated bowel loop (asterisk) behind pectineus muscle. B, T2-weighted MR imaging confirms incarcerated obturator hernia (asterisk). Also note contralateral asymptomatic hernia. a = femoral artery, v = femoral vein. Fig. 8.-Inflamed appendix in unusually high position. A, Sonogram shows inflamed appendix in right upper quadrant. B. In view of its unusual position, location of appendix was drawn on skin with indelible pencil. C. This location influenced site, size, and direction of incision. 182 AJR:168, January 1997

5 Sonography and the Acute Abdomen from findings immediately after such an episode and from the findings several days after such an episode. For instance, if a patient is examined during an episode of biliary colic, a sonogram may show hydrops, thickening of the gallbladder wall, a sonographic Murphy s sign, and an impacted stone. A few days later, when the symptoms have subsided, all that is found is a morphologically normal gallbladder containing a mobile stone. Sonographic findings should always be correlated with the course of the symptoms in time. Dilatation due to an obstruction ofthe gallbladder, kidney, bowel, or appendix may disappear quickly after relief of the obstruction. However, the inflammatory changes associated with the process of obstruction often remain sonographically visible for days or weeks even when the symptoms have long since subsided. These residual changes explain why an impressive cholecystitis or appendicitis can be documented sonographically in a patient free ofsymptoms at the time of the sonogram 16](Fig. I1). Preferably, the examination should be done during an episode of pain for two reasons. Not only is the chance of a diagnostic sonographic finding greater but it also guarantees optimal timing of possible surgery. In case of intennirtent episodes ofpain, the patient should be warned to seek immediate medical attention during the next episode so that sonography, and possibly surgery, can be performed without delay (Fig. 12). Sonographically Guided Puncture In patients with an acute abdomen, a small amount of free fluid may occur in both surgical and nonsurgical conditions and, as such, is nonspecific. Identifying the nature of the Fig. 9.-Acute gallbladder hydrops. A and B, On compression of gallbladder, in longitudinal (A) and transverse (B) plane mild bulging (arrowheads) of anterior abdominal wall was noted, indicating hydrops with high pressure in lumen. No gallstones were visualized. At surgery, 3-mm obstructing stone in distal cystic duct was found. fluid, however, can be helpful. Sonographically guided puncture carries virtually no risk and allows rapid differentiation between blood, pus, and bile, and additional laboratory investigation can distinguish further between gastric fluid, pancreatic fluid, and malignant ascites (Fig. 13). Indirect Sonographic Findings Many sonographic diagnoses such as appendicitis, renal colic, or cholecystitis are fairly straightfoaward and can be made with confidence. However, sometimes the primary condition is not well, or not at all, recognizable by sonography. In such cases, indirect sonographic findings may be of help. Fig. 10.-Small-bowel obstruction with partially gas-filled loops. Fig year-oldwomanwith classic signs of chole- A and B, Ventral scanning yielded only air(a), whereas posterolateral scanning clearly showed dilated loops (B). cystitis 2 days earlier was completely free of symptoms when this sonogram was obtained. Gallbladder still showed considerable residual changes. AJR:168, January

6 Puylaert et al. Fig. 12.-Over 3 months, 59-year-old woman suffered from severe colicky attacks lasting 1-2 hr. Two earlier sonographic examinations performed during symptom-free intervals showed no abnormalities. Present examination, performed during attack, revealed intussusception. primary bowel wall diseases as infectious ileocolitis. Crohn s disease, or ischemia I 15). Other useful indirect findings are associated with abscesses, which occur when a gastrointestinal perforation is not effectively sealed off. Often the underlying causeappendicitis, diverticulitis, Crohn s disease, or a malignancy-can be determined. In cases of large, gas-containing abscesses, this determination may be difficult I 16, 17). An abscessogram done some days after percutaneous drainage and a repeated sonogram may, as yet, reveal the underlying condition. Another indirect sonographic sign is related to free perforation. If the process of sealing the bowel has been completely ineffective and the bowel contents are spilling into the peritoneal cavity. first a local and then a generalized peritonitis with paralytic ileus will ensue. The presence of dilated fluid-filled bowel loops with absent peristalsis is an important clue and. in most cases, indicates a gastrointestinal perforation requiring surgical treatment (Fig. 15). The most helpful indirect findings are related to gastrointestinal pertration. such as may occur in appendicitis, diverticulitis. Crohn s disease, peptic ulcer disease, and bowel cancer. In all of these conditions, protective migration of omentum, inesenteiy, and bowel loops to the site of imminent perthration occurs in an attempt to seal offand prevent spillage of howel contents into the peritoneal cavity. The migrating, inflamed fatty mesentery and omentum are recognized as amorphous masses of hyperechoic, noncompressible tissue. This inflamed fat is usually concentrated around the diseased organ and, although often prominent, can easily be overlooked on a sonogram. The most conspicuous feature of inflamed fat is its noncompressibility, which is best observed by applying intermittent graded compression with the transducer. Inflamed fat, especially in advanced cases, is well recognized on a CT scan as hyperattenuating streaky (dirty) areas in the abdominal fat(dirtyfat)(fig. 14). Secondary mural thickening of the neighboring bowel loops, such as seen in appendicitis, is another indirect sign. This finding can be confusing and may be interpreted as such Normal Sonographic Findings It is not unusual to find no sonographic abnormalities whatsoever in patients with an acute abdomen. In patients with a low clinical suspicion of disease requiring surgery, a negative sonographic examination can usually be taken as confirmation that no condition requiring surgery exists. lf however, clinical findings and laboratory tests suggest a serious abnormality, further workup is required. This problem occurs frequently in young women in whom appendicitis must be differentiated from adnexi- Fig year-old woman was admitted with rapidly increasing pain over entire abdomen. She had suffered no trauma. A and B, Sonograms show free fluid around liver and inhomogeneous spleen. C, Sonography-guided puncture yielded blood. Surgery confirmed spontaneously ruptured spleen. 184 AJR:168, January 1997

7 Sonography and the Acute Abdomen Fig. 14.-Inflamed fat in sigmoid diverticulitis. A, Sonogram shows wall thickening of contracted sigmoid (5) and diverticulum surrounded by large areas of hyperechoic, noncompressible tissue (asterisks). B, This tissue represents fatty mesentery and migrated omentum, which was confirmed by CT scan. unnecessary laparotomy. Thickening ofthe pyelocaliceal wall and local tenderness over the kidney may provide clues to the diagnosis [ I 8J. Two other diseases that initially do not give rise to abnormal sonographic findings are pancreatitis and mesenteric ischemia [19). Pancreatitis is usually diagnosed by an elevated amylase level in both urine and serum. Mesenteric ischemia, however, can be a diagnostic nightmare. When no sonographic abnormalities are found in a patient with severe epigastric or upper quadrant symptoms, a myocardial infarction or a pulmonary cause should be considered. A subtle amount of pleural fluid or a region of pulmonary consolidation may be the first clue to the diagnosis of pulmonary embolism or early pneumonia (Fig. 16). If, in a patient with severe abdominal symptoms, both sonographic and laboratory findings are repeatedly normal. a psychogenic cause or functional bowel disorder should be suspected. If the sonographic examination is not conclusive, the most useful complementary study is a CT scan, especially if the patient is obese or is not suitable for sonography in other respects. Communication with the Clinician A Fig. 15.-i 1-year-old girl presented with right lower quadrant pain. A and B, Sonograms show dilated fluid-filled bowel loops over entire abdomen with complete absence of penstalsis during 10 mm of examination. No other abnormality was shown. Surgery by median incision showed generalized purulent peritonitis from perforated appendicitis. tis. Normal sonographic findings do not exclude appendicitis or adnexitis. In this context, the role of the erythrocyte sedimentation rate must be emphasized, because in adnexitis it is usually high at the time of admission. If the etythrocyte sedimentation rate is markedly elevated in a young and not too obese woman with normal sonographic findings. adnexitis is strongly favored. The reasoning is as follows: if the high erythrocyte sedimentation rate had been caused by appendicitis, conspicuous and extensive inflammatory periappendiceal changes would be present that would not have gone unnoticed during sonography. Another condition in which no sonographic abnormalities are found in the presence ofa high erythrocyte sedimentation rate is pyelonephritis; however, this diagnosis is usually made on clinical presentation. It can, however, masquerade as a condition requiting surgery and lead to an B For mote than a century, surgeons have been taught to rely on their clinical impression in their decision between surgery and conservative management of patients with an acute abdomen. Understandably, surgeons have viewed the advance ofsonography in this field with caution and perhaps even some distrust. The realization that clinical astuteness is being challenged by technology has c&tsed both excitement and confusion [20}; therefore, radiologists must have a good relationship with surgeons. A good relationship starts with mutual confidence and good communication. Radiologist and surgeon should speak acornmon language. Tenns such as phlegmon, perforation, walled-offperforation, pseudoaneulysm, and ileus can mean differentthings to a surgeon and a radiologist In difficult cases, therefore, a morphologic description of the intniabdominal situation based on the sonographic findings should be given, and a single-term diagnosis should be avoided. ln such cases, the radiologisi should ask the surgeon to be present at the sonographic examination. In the final report, the sonographic findings should be integrated with the patient s history, physical signs, and laboratory data as well as the results of a possible CT scan AJR:168, January

8 Puylaert et al. Fig O-year-old woman presented with severe right upper quadrant pain and marked leukocytosis. Patient was suspected of having cholecystitis or generalized pelvic inflammatory disease. A, Sonographically. abdomen was normal. Only abnormalities observed were some echolucent areas above diaphragm. B, On lateral chest radiograph, small posterobasal consolidation wasfound. Final diagnosis was right-sided basal pneumonia. and other radiologic examinations. Liberal use and a clinical approach are the key points in sonography of the acute abdomen. Sonography is a valuable tool to lower both the number of unnecessary laparotomies and the technique related to surgical delay. References I. Pieper R. Kager L, Nesman P. Acute appendicitis: a clinical study of 1028 cases of emergency appendectomy. Acw Chir Scand 1982; 140: Schwerk WB, Wicktrup B, Rothmund M, Ruschoffi. Ultrasonography in the diagnosis of acute appendicitis: a prospective study. Gastroenterologv 1989:97: Marston WA, Ahlquist R, Johnson G, Meyer AA. J VascSurg 1992:16: Puylaert JBCM. Rutgers PH. Lalisang RI, et al. A prospective study of ultrasonography in the diagnosis of appendicitis. N Engi J Med 1987; 317: Braun B, Blank W. Ultraschall-Diagnostik der Akuten Appendizitis. Ultraschall 1989: 10: 17()-l76 6. Ooms HWA. Ho Kang You PJ, Koumans RKJ, Puylaert JBCM. Ultrasound and appendicitis. Br JSurg 1991:78: Broekman BAMW, Puylaert JBCM, Van Dessel 1. Sigmoid diverticulitis in the female: transvaginal sonographic findings. J C/in Ultrasound 1993; 2 1: Puylaert JBCM. Transvaginal sonography for appendicitis (letter). AJR 1994:163: Puylaert JBCM. Rightsided segmental omental infarction: clinical, US and CT findings. Radiol- Og) 1992;l84: Rioux M, Langis P. Primary epiploic appendicitis: clinical, US and CT findings in 14 cases. Radiolog% 1994:191: I I. Lohle P. Coerkamp EG. Puylaert JBCM. Hermans E. Nonpalpable rectus sheath hematoma clinically masquerading as appendicitis: US and CT diagnosis. Abdom Imaging 1995:20: Schwerk WB, Schwarz 5, Rothmund M. Sonography in acute colonic diverticulitis: a prospective study. Dis Colon Rectum 1992:35: I 3. Wilson SR. The value of sonography in the diagnosis of acute diverticulitis of the colon. AiR 1990:154: Puylaert JBCM. Acute appendicitis: US evaluation using graded compression. Radiology 1986: 158: IS. Puylaert JBCM. Vermeijden Ri, Van der WerfSDJ, Doornhos L, Koumans RKJ. Incidence and sonographic diagnosis of bacterial ileocaecitis masquerading as appendicitis. Lrnicet l989:ii: Jeffrey RB. The pancreas. In: Jeffrey RB. ed. CT and sonographv of the acute abdomen, 1St ed. New York: Raven. 1989: Balthazar El. Gordon RB. CT of appendicitis. Semin Ultrasound CT MR 1989; 10: Avni EF. Van Gansheke D, Thona Y. et al. US demonstration of pyelitis and ureteritis in children. Pediatr Radio! 1988:18: Jeffrey RB. Management of the periappendical inflammatory mass. Seinin Ultrasound CT MR 1989;10: Schwartz SI. Tempering the technological diagnosis ofappendicius. N EnglJ Med 1987:317: AJR:168, January 1997