Clinical Ivestigation

The Predictive Value of Physical Examinations for Ascites STEVEN CUMMINGS, MD; MAXINE PAPADAKIS, MD; JANE MELNICK, MD; GRETCHEN A. W. GOODING, MD, and LAWRENCE M. TIERNEY, Jr, MD, San Francisco

To determine the predictive value ofphysical signs forascites, we compared the results ofphysical examination with those of abdominal sonography in 90 men in hospital with liver disease. The positive predictive values ofshifting dullness andprominent fluid waves were low (51% and 73%). We divided the patients into two groups: those with prolongedprothrombin times (72% prevalence of ascites by sonogram), and those with normal prothrombin times (15% prevalence). In patients with prolongedprothrombin times, a prominent fluid wave had a very high positive predictive value for ascites (96%). Many patients with prolonged prothrombin times had ascites despite negative physical signs. In contrast, in those with normal prothrombin times, both shifting dullness and prominent fluid waves were usually falselypositive. Patients with normalprothrombin times and no shifting dullness rarely (2%) hadascites. The predictive value of physical signs for ascites depends on the prevalence of ascites in groups of patients that are examined. The prothrombin time is a useful index for identifying inpa- tients with a high orlowprevalence ofascites andthepredictive value ofphysicalsigns is enhanced byinterpreting them in combination with a patient'sprothrombin time. (Cummings S, Papadakis M, Melnick J, et al: The predictive value of physical examinations for ascites [Clinical Investigation]. WestJ Med 1985 May; 142:633-636)

The predictive value of diagnostic tests for a specific dis- ascites and to determine whether dividing patients into sub- order depends on the prevalence of that disorder in the groups with a high or low prevalence ofascites could improve patients who undergo the test. This principle has been applied the interpretation ofthese physical signs. to a variety oflaboratory tests but has not been widely applied Ascites is an important finding in patients with liver dis- to the physical examination.I According to this principle, in ease. The presence of ascites predicts cirrhosis in patients patients who have a low prevalence of the disorder, positive who have chronic active hepatitis,4 has prognostic signifi- diagnostic physical findings are more likely to be "false posi- cance in patients who have chronic liver disease5 and is an tives" than findings in patients who have a higher prevalence important factor in determining the risk of surgical proce- ofthe disorder. The predictive value ofdiagnostic tests can be dures in patients with liver disease.' Because spontaneous improved by identifying subsets of patients who have a high bacterial peritonitis is also liable to develop in patients with or low prevalence ofthe disorder. This concept has been very ascites, physical findings of ascites often lead to urgent diag- fruitfully applied, for example, to interpretation of exercise nostic paracentesis in febrile patients. testing for coronary artery disease.2 We believe that a similar Until the advent of abdominal ultrasonography, ascites strategy might improve the interpretation of some aspects of was diagnosed primarily by physical examination and abdom- physical examinations. inal paracentesis. Physical examination is an immediate and Many physicians regard physical findings for ascites as inexpensive way to detect ascites, but the predictive value of unreliable. Therefore, we undertook this study to detennine individual physical findings is uncertain. One study has re- the predictive value of commonly used physical signs for ported that classic physical findings had relatively low predic-

From the Division ofGeneral Internal Medicine, University ofCalifornia, San Francisco, School ofMedicine, and the Medical and Radiology Services, Veterans Administration Medical Center, San Francisco. Accepted, revised, February 24, 1985. Reprint requests to Steven Cummings, MD, Division ofGeneral Intemal Medicine, UCSF, RoomA-405, 400Parnassus Ave, San Francisco, CA 94143.

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tive values for ascites in a small group ofpatients.3 Although of instances. Therefore, for the analysis, ratings of slight and the accuracy ofabdominal sonography in detecting ascites has absent were combined, and fluid waves were considered not been thoroughly investigated, some studies have sug- present only ifrated as "prominent." gested that sonograms are very sensitive and specific for as- Before the study began, the three examiners evaluated cites. Static sonograms detect as little as 100 ml of ascitic several nonstudy subjects for the physical signs of ascites to fluid7 and, especially when real-time examinations are used, standardize their methods and judgments. A fourth investi- false-positive sonograms for ascites appear to be uncommon.8 gator observed each examiner's technique at the beginning However, abdominal sonograms are not always immediately and the end of the study. This investigator detected no differ- available and they are relatively expensive; the charge is ence among the examiners in techniques and no changes in customarily between $120 and $200. techniques over the course ofstudy. Therefore, to determine the predictive value of common Each patient underwent both static and real-time abdom- physical signs for ascites, we prospectively compared inal sonography. Each subject was scanned supine in the para- common physical signs with the findings from abdominal sagittal and the transverse planes. If ascites was present, the sonograms in men in hospital with liver disease. To determine amount was rated on a scale from slight (1+) to massive the effect of the prevalence of ascites on the predictive value (4+). The sonograms were read by a staff radiologist who of the physical findings we divided the patients into two was unaware ofthe results ofthe physical examinations. groups: one group with prolonged prothrombin times who Each patient's current prothrombin time and the presumed had a very high prevalence of ascites and a second group with cause of his liver disease was recorded from the medical normal prothrombin times who had a much lower prevalence record by the investigator who did not participate in either the ofascites. physical examinations or interpretation ofthe sonograms. We hypothesized that a prolonged prothrombin time, a marker of Patients and Methods advanced hepatocellular dysfunction,9 would be associated We recruited patients for the study from the Inpatient with a higher prevalence of ascites. Prothrombin times were Medical Service of San Francisco Veterans Administration determined by the Quick method using a Simplastin reagent. Hospital. To identify all eligible patients, we systematically Normal upper limit for the laboratory during the period ofthe contacted house officers on the day after they received admis- study was 12 seconds; therefore, we defined a prothrombin sions and at the morning reports and periodically surveyed time as abnormal ifit exceeded 12 seconds. charts of patients on the medical service. Patients were in- We analyzed the data from each examiner separately and cluded in the study if they had any two of the following signs then, to determine overall sensitivity, specificity and predic- of liver disease: (1) elevated serum alkaline phosphatase con- tive value of signs, we pooled data from all examinations for centration, (2) elevated direct serum bilirubin value, (3) ele- each sign. We used standard definitions of sensitivity, speci- vated serum aspartate amino transferase or alanine amino ficity and predictive value': sensitivity defined as the propor- transferase level, (4) liver span greater than 12 cm by exami- tion of patients with ascites by sonogram who had a positive nation. Suspicion that ascites was present was not a criterion sign, specificity as the proportion without ascites who had a for inclusion in or exclusion from the study. Patients were negative sign, and positive predictive value as the proportion excluded if they had had an abdominal surgical procedure with a positive sign who had ascites. We calculated confi- within the previous month, or were unable or unwilling to dence intervals for proportions, and we used McNemar's test undergo either physical examination or abdominal sono- to determine whether there were significant differences be- graphy. Enrollment was continued until each examiner had tween individual examiners in the sensitivity or specificity of completed 60 examinations. their physical examinations. We also carried out multiple Each of the patients was examined by two examiners for logistic regression analyses to determine whether the addition four signs of ascites: shifting dullness, fluid waves, bulging of other physical signs would further improve the predictive flanks and abdominal distention. Three examiners partici- value ofthe physical examination. pated in the study, all board-certified internists: a fellow in This study was approved by the Committee on Human general internal medicine, a chiefresident in medicine and the Experimentation at the University of California, San Fran- assistant chief of the medical service. The examiners were cisco. unaware of each other's findings, the results of a patient's abdominal sonogram and a patient's prothrombin time. All Results physical examinations were done within 72 hours ofthe sono- Ninety men with liver disease underwent two physical gram. examinations and abdominal ultrasonography. Their liver Shifting dullness was sought by percussing the patient's disease was most often attributed to excessive consumption of right flank with the patient first lying flat and then lying in the alcohol (Table 1). Thirty patients (33 %) had ascites shown by right lateral decubitus position supported by a 45-degree- abdominal sonography. The ascites was rated as massive angle foampillow. Shifting dullness was deemed present ifthe (4+) in 3, mild (2 +) or moderate (3 +) in 20 and slight (1+) levels at which dullness was detected differed by at least 1 cm. in 7 patients. Fluid waves were sought by sharply tapping each flank while The most sensitive sign for ascites was shifting dullness an assistant pressed the edge of his hand longitudinally into and the most specific was a prominent fluid wave (Table 2). the abdomen. The examiners rated fluid waves as absent, Both examiners agreed about the presence or absence of slight or prominent. However, they often disagreed about the shifting dullness in 78%, prominent fluid waves in 76%, presence of "slight" fluid waves. When one examiner rated a bulging flanks in 79% and abdominal distention in 86% ofthe fluid wave as "slight," the other rated it as "absent" in 61 % examinations. There were no significant differences in the

634 THE WESTERN JOURNAL OF MEDICINE PHYSICAL EXAMINATION FOR ASCITES sensitivities and specificities of any of the physical signs be- by ultrasonography. The predictive values we found are sim- tween individual examiners (P> .2 for all pairs of examiners ilar to those reported by Cattau and co-workers3 for a small by McNemar's test). group ofinpatients who had a 28 % prevalence ofascites. However, our study also shows that the interpretation of Predictive Values of Physical Signs these physical signs for ascites depends on the prevalence of Overall, the predictive values of physical signs were low. ascites in the type of patient examined. We found that the The positive predictive value of shifting dullness for ascites subgroup ofpatients with a prolonged prothrombin time had a was 51 % and for a prominent fluid wave was 73 % (Table 2). high (72%) prevalence of ascites. In these patients, positive All three examiners had very similar positive predictive physical findings almost always correctly identified the pres- values for shifting dullness (55%, 52%, 50%) and a promi- ence of ascites. In particular, the presence of a prominent nent fluid wave (74%, 67%, 75%). The combination of fluid wave in a patient with a prolonged prothrombin time had shifting dullness and a prominent fluid wave had a 77% pre- a very high (96 %) predictive value for ascites. dictive value for ascites which was not significantly different from the predictive value ofa fluid wave alone. These physical findings were almost always positive when amount of ascites was massive or moderate; shifting dullness was present in 100% and prominent fluid waves in 89%. But physical signs were usually absent when the amount ofascites was slight; shifting dullness was present in 43% and fluid waves in 21 %. Of the seven patients with slight amounts of ascites, six had prolonged prothrombin times. Prothrombin Times, Prevalence of Ascites and Predictive Values of Physical Signs To determine the effect of the prevalence of ascites on the TABLE 2.-OveIIS SeicyandPositive predictive values of shifting dullness and prominent fluid Predictiv Vakie Wiys41clTVP4'- n fodrAscifte waves we divided the patients into two groups: 31 patients with prolonged prothrombin times and 59 patients with normal prothrombin times. Two of the patients who had pro- longed prothrombin times were receiving coumadin and were excluded from further analysis. Of the remaining 29 patients ...... with prolonged prothrombin times, 21 (72 %) had ascites. Of *'' .' * ' ...... >e ...... 46''. . '. the 59 patients with normal prothrombin times, 9 (15 %) had ascites. Positive physical signs were generally correct in pre- dicting ascites in patients with prolonged prothrombin times. Proportion of Patients With Ascites However, in patients with normal prothrombin times, posi- .,.,''.".)'...... '' Sign Present Sign Absent tive signs were usually false-positives (Figure 1). For ex- ample, the predictive value of a prominent fluid wave was .82 96% in patients with prolonged prothrombin times, but only (.70 - .93) 48 % in patients with normal prothrombin times. Negative physical signs were generally accurate in pre- .43 dicting the absence of ascites in patients with normal pro- Shifting (.17 - .49) .29 thrombin times. For example, when no shifting dullness was Dullness (.16 - Al) m .02 detected in patients with normal prothrombin times, ascites - .05) was rarely (2%) present (Figure 1). However, in patients to with prolonged prothrombin times, negative signs were often falsely negative. When no shifting dullness was detected in * Prolonged PT patients with prolonged prothrombin times ascites was .96 present, nevertheless, in 43 %. 67 - .") U Normal PT The combination of a prominent fluid wave and a pro- longed prothrombin time had the highest predictive value for ascites (96%). The combination of the absence of shifting .28 Fluid (.24 .9) dullness and a normal prothrombin time virtually excluded Wave - ascites. No other combinations of findings had better predic- tive values. - -.06) Discussion EA " .314) We found that the predictive value of common physical Figures In parenthesis represnt 95% confidence intrvals. signs for ascites was low in a group of90 men in hospital with Figure 1.-Predictive value of physical signs for ascites in patients liver disease, who had a 33 % prevalence ofascites as detected with normal and prolonged prothrombin times.

MAY 1985 * 142 * 5 635 PHYSICAL EXAMINATION FOR ASCITES

In the subgroup with a normal prothrombin time, negative tests may also serve to identify subgroups of patients with a physical signs quite accurately predicted the- absence of as- high-or low prevalence ofascites. cites. In particular, the absence of shifting dullness and These findings illustrate how the predictive value ofphys- normal prothrombin time virtually excluded ascites (Figure ical diagnostic signs, like that of other types of diagnostic 1). tests, depends on the prevalence ofte disorderbeing sought.1 Based on these findings, we believe that the combination We believe, that this principle can also be usefully applied to of a carefully carried out physical examination and a pro- other physical diagnostic signs. The positive predictive value thrombin time can guide a more selective use of abdominal of physical signs will be higher when the disease is prevalent sonography. First, patients admitted to hospital who have and lower when the disease is uncommon or unlikely. liver disease, prolonged prothrombin times and a prominent We cotclude that in unselected men in hospital with liver fluid wave are very likely to have ascites and generally do not disease, physical signs of ascites, by themselves, are often require sonography for confirmation. Second, patients who misleading. Patients' prothrombin times are a useful index of have liver disease but who have a normal prothrombin time the prevalence of ascites and the utility of physical signs for and no shifting dullness are very unlikely to have ascites. ascites can be substantially improved by interpreting these Sonography to exclude ascites seldom will be necessary. physical signs in combination with the patients' prothronmbin Third, shifting dullness or prominent fluid waves in patients times. who have, normal prothrombin times often will be falsely positive for ascites and abdominal sonography may be needed REFERENCES to settle the issue and should be done before paracentesis is 1. Griner PF, Mayewski RJ, Mushlin Al, et al: Selection and interpretation of diagnostic tests and procedures: Principles and applications. Ann Intern Med 1981; attempted. Finally, many patients in hospital with liver dis- 94:553-600 ease and prolonged prothrombin times have ascites despite the 2. Rifkin RD, Hood WB Jr: Bayesian analysis of electrocardiographic exercise stress testing. N Engl J Med 1977; 297:681-686 absence ofphysical signs of ascites. Some clinical situations, 3. Cattau EL. Benjamin SB, KnuffTE, et al: The accuracy ofthe physical examina- such as unexplained fever, may warrant sonography to ex- tion in the diagnosis ofsuspected ascites. JAMA 1982; 247:1165-1 166 clude ascites. 4. Czaja AJ, Wolfe AM, Bagenstoss AH: Clinical assessment ofcirrhosis in severe chronic active liver disease: Specificity and sensitivity ofphysical and laboratory find- Since'we studied a group of men in hospital with a high ings. Mayo Clin Proc 1980; 55:360-364 (33%) prevalence of ascites, our findings may not be com- 5. Borowsky SA, Strome S, Ott E: Continued heavy drinking and survival in alcoholic cirrhotics. Gastroenterology 1981; 80:1405-1409 pletely applicable to other clinical settings. For example, the 6. Brown FH, Yih-Fu S, Richter GC: Anaesthesia and surgery in the patient with positive predictive values of these physical signs are likely to liver disease, In Goldman DR, Brown FH, Levy WK, et al (Eds): Medical Care ofthe be lower in outpatient settings where ascites is less prevalent. Surgical Patient. Philadelphia and Toronto, Lippincott, 1982, pp 326-342 7. Goldberg BB, Goodman G, Clearfield HR: Evaluation of ascites by ultrasound. The physical examinations were done in a standardized Radiology 1970; 96:15-22 manner and examinations carried out less rigorously may be 8. Gefter WB, Arger PH, Edell SL: Sonographic pattems ofascites. Semin Ultra- sound 1981; 2:226-232 less accurate. We did not analyze the value ofother biochem- 9. Combes B, Shenker S: Laboratory tests, In SchiffL, SchiffER (Eds): Diseases of ical tests in the diagnosis ofascites and it is possible that other the Liver, 5th Ed. Philadelphia and Toronto, Lippincott, 1982, pp 259-302

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