Brief Reports

Clinical guidelines, computed tomography scan, and negative appendectomies: a case series

Chad Harswick MD, Amy Archer Uyenishi MD,

Mary Frances Kordick PhD, RN, Shu B. Chan MD, MS*

Resurrection Emergency Medicine Residency Program, Resurrection Medical Center, Chicago, IL 60631, USA

Received 19 July 2005; accepted 26 July 2005

Abstract

Introduction: Prior studies suggest that preoperative Abdominal computed tomography (CT) scan can contribute to a low Negative appendectomy rate. Our study objective was to evaluate cases of negative appendectomies for clinical criteria and CT use.

Methods: Retrospective 1-year study of all negative appendectomies at a community hospital. Data included clinical evidence for appendicitis as well as CT results if performed.

Results: Of 122 cases reviewed, 8 (6.6%) were negative appendectomies. Six were younger than 20 years. Four had a preoperative CT scan. Overall, 106 (87%) of 122 cases received preoperative CT and had a negative appendectomy rate of 3.8%. Sixteen cases did not have preoperative CT and had a negative appendectomy rate of 25% (odds ratio, 8.5; 95% confidence interval, 1.9-38.5; Fisher exact test P = .01). Conclusion: Patients who had a CT scan for suspected appendicitis had a lower rate of negative appendectomies than those who had no CT. Most of the negative appendectomies occurred in patients younger than 20 years.

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Introduction

Acute appendicitis is the most common surgical emer- gency, with approximately a quarter of a million patients undergoing appendectomy per year [1-6]. It is imperative that patients with appendicitis go to the operating room early, as there is a significant increase in morbidity and mortality in those experiencing appendiceal rupture [7-11].

Presented at the Illinois College of Emergency Medicine, Spring Symposium; March 3, 2005; Chicago, Ill.

* Corresponding author. Tel.: +1 773 594 7816; fax: +1 773 594 7805.

E-mail address: [email protected] (S.B. Chan).

Diagnosing appendicitis based on clinical grounds can be difficult, however, and historically accepted rates of negative appendectomy (normal appendix) found at surgery are approximately 20% [5,7,8,12-18].

Over the past few decades, attempts were made to improve the diagnostic accuracy in cases of suspected appendicitis through the use of radiological adjuncts. The ideal test would need to be sensitive so that one could be confident in the decision to bypass the OR if the test was negative. It would also have to be specific, so a positive test would not lead to a fruitless trip to the OR, resulting in a negative appendectomy. Providing an alternative diagnosis in the event of a negative test is also a desirable quality of

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such a test. Although abdominal computed tomography and Abdominal ultrasound were both investigated in this function, the evidence has clearly shown CT to be the superior modality [5,9,15,17].

Numerous studies have shown CT scanning to be more than 95% sensitive and specific in diagnosing acute appendicitis [5,6,8-11,15,19]. A landmark study by Rao et al [6] noted that the use of CT in suspected appendicitis would lead to improvED patient care and lower costs. Since that time, many authors note a dramatic increase in the use of CT in suspected appendicitis [5,10,14,20].

Once it became clear that CT was an accurate test for appendicitis, the question shifted to its clinical relevance. Although it was shown that the inherent delay in obtaining the CT did not lead to an increase in the perforation rate, perforation tends to be dependent on delay in initial presentation to the hospital [7,8,12-14]. Many studies show that those patients who undergo CT have a negative appendectomy rate that is lower than the previously accepted 15% to 30% [4,5,7,8,10,12,16,18-21]. The ques- tion that is currently debated is whether the use of CT decreases the negative appendectomy rate. Some argue that using CT decreases the negative appendectomy rate, whereas others note that, even as the numbers of CT scans obtained have increased tremendously, there has not been a corresponding decline in the negative appendectomy rate [4,5,7,8,10,12,14,16,19-21].

On reviewing the literature, it became clear that most investigators were using CT for equivocal cases only. Those patients who present with classic signs of appendi- citis were sent directly to the OR, whereas those whose presentation was not judged to be straightforward received CT. In most cases, there was no set criterion for an equivocal determination– it was based on clinical judge- ment. It became apparent that, in almost every study, patients who actually had a CT had a lower negative appendectomy rate than has been accepted, generally less than 10% [4,5,7,8,10,12,16,18-21].

These data from multiple studies beg the question bif the clinical criteria we have traditionally used to diagnose acute appendicitis are relatively inaccurate, having led to a 20% false-positive rate and the associated surgical complications, why are clinicians clinging to these criteria when a relatively inexpensive highly accurate test is available? Q In other words, it would seem only logical to demand that, to use these clinical signs to go directly to the OR and bypass CT, they must be shown to be as effective as CT. They should be shown to produce the less than 10% negative appendectomy rate that has been achieved by using CT.

This study had 2 aims. The first was to compare the negative appendectomy rates of patients who had a CT scan to those who did not have CT. This study also aimed to retrospectively evaluate the clinical criteria presented by Paulson et al [22] for when to take a patient with suspected appendicitis to the OR without first obtaining a CT scan of the abdomen. The authors state:

A patient, male or female, who presents with acute abdominal pain that has migrated from the umbilicus to the right lower quadrant and that is associated with tenderness in the right lower quadrant should be taken directly to the operating room for an appendectomy. The expected diagnostic accuracy in these circumstances approaches 95% and is probably not improved by imaging [22, p241].

In this study, the charts of patients who had an appendectomy but a normal appendix were reviewed for the clinical criteria for classic presentation of appendicitis. The clinical criteria include Short duration of pain, abdominal rigidity, migration of pain to right lower quadrant (RLQ), pain centered in RLQ, RLQ tenderness, and anorexia [22].

Methods

After approval from the institutional review board was obtained, cases were chosen from a list generated from pathology department records. This list contained all appendices sent by surgeons to the pathology department for a reading from January 1, 2003 to December 31, 2003. Included were all patients receiving appendectomy for suspected appendicitis during the study time frame at a community hospital with 434 beds and 37000 annual emergency department (ED) visits. Excluded were the medical records of any patient whose appendix was removed incidentally while receiving surgery for an indication other than suspected appendicitis (for instance, an Exploratory laparotomy for chronic pain or concurrently with another primary operation such as a hemicolectomy or ovarian cystectomy). For each patient, the primary and senior investigators reviewed the final pathology reports concurrently, and, by consensus, each record was marked bpositive appendicitis,Q bnormal appendix,Q or bincidental appendectomy.Q An emergency physician blinded to the study protocol and hypothesis reviewed any disagreements. The incidental appendectomies were then excluded from further study. The final Radiology reports were also concurrently reviewed in a similar fashion and categorized as bpositive,Qbnegative,Qbquestionable,Q or bnondiagnostic.Q The extent of CT use, as well as negative appendectomy rates with CT, without CT, and in total, was calculated. Those records marked bnormal appendix Q were then submitted to medical records, and the entire chart was reviewed and abstracted by the primary investigator for these 6 criteria: short duration of pain (b 24 hours), abdominal rigidity, migration of pain to RLQ, pain centered in RLQ, RLQ tenderness, and anorexia. Only criteria documented by physicians were abstracted. Any criteria not specifically documented were considered not present for the summary analysis. The results are presented as a case series. All CT scans for suspected appendicitis were performed with intravenous contrast, 2 hours after the patient completed

consumption of oral contrast. Each CT scan performed through the ED received a preliminary report. All CT scans had a final reading by an attending radiologist.

Results

There were 138 appendectomies performed during the 1-year study time frame. Of these, 16 incidental appendec- tomies were excluded from further study, leaving 122 cases. There were 8 negative appendectomies, for a negative appendectomy rate of 6.6%. Before operation, 106 patients (87%) had a CT scan of the abdomen. Four of these patients had a negative appendectomy, for a negative appendectomy rate of 3.8%. In contrast, 4 of 16 patients who had no CT before operation had negative appendectomies, or 25% negative appendectomy rate without preoperative CT (odds ratio, 8.5; 95% confidence interval, 1.9-38.5; Fisher exact test P = .0103). Of the 122 appendectomies included, there were 2 cases with CT reports bnegativeQ for appendicitis. Both cases were pathological positive and not included in the negative appendectomy case series. For the 8 patients in the case series, the majority had 4 or more of the 6 clinical criteria present. All 8 patients were younger than 39 years, and 6 were younger than 20 years. Fifty percent (4/8) had preoperative CT. Of those with preoperative CT scans, one was bnondiagnostic and one was questionable.Q Two others had preliminary results that were more suggestive of appendicitis than the final reading.

• 1. Negative appendectomy case series
     1. Case 1

A 3-year-old girl was directly admitted to pediatric unit (no ED visit) for 1 day of generalized abdominal pain. General surgery was consulted on hospital day 1. Two of the 6 clinical criteria, short duration of pain and anorexia, were present. Abdominal rigidity was not present, and 3 additional criteria were not recorded: migration of pain to RLQ, RLQ tenderness, and pain centered in RLQ. Generalized pain and suprapubic tenderness were noted, as was elevated white blood cell count. A CT scan was not performed. The patient was taken to the OR on hospital day 1; surgery note indicated bappendix injected and inflamed,Q but histology was normal.

• • 1. Case 2

A 35-year-old man presented to the ED at 3:30 pm complaining of awakening that morning with periumbilical pain. Five of the 6 clinical criteria were noted in the medical record. Only abdominal rigidity was not recorded. CT was ordered by the ED resident but cancelled by surgery, and the patient was taken directly to the OR. The pathology report stated bno histological evidence of acute appendicitis,Q although bfecal stasis with a minute area of intraluminal mucopurulent exudation, seen in one tissue block only Q was noted.

• • 1. Case 3

A 14-year-old girl presented to the ED at 1:43 pm with abdominal pain. Four of the 6 clinical criteria were present. Migration of pain to RLQ was not present, and abdominal rigidity was not recorded. CT scan was not performed. Patient was taken directly to the OR for appendectomy, and the appendix was normal.

• • 1. Case 4

An 11-year-old girl was directly admitted to the hospital with abdominal pain. Three of the 6 clinical criteria were present–short duration of pain, pain centered in RLQ, and RLQ tenderness. Anorexia was not present. Abdominal rigidity and migration of pain were not recorded. No CT was performed. Histology showed lymphoid hyperplasia of the appendix and chronic focal periappendicitis, but no appendicitis.

• • 1. Case 5

A 38-year-old man presented to the ED at 8:17 am with abdominal pain and emesis. Four of the 6 clinical criteria were noted. Short duration of pain was not present (3 days per surgery attending note), and abdominal rigidity was not recorded. CT scan was obtained, but was nondiagnostic– bthickening of terminal ileum, Appendix not visualized, no free fluid, mesenteric fat questionably indurated diffusely.Q The patient was taken to the OR that day, and the appendix was normal.

• • 1. Case 6

A 19-year-old man presented to the ED at 2:50 pm complaining of RLQ pain of 3 days’ duration which started there and remained there. Only 2 of the 6 clinical criteria (pain centered in RLQ and RLQ tenderness) were present. Duration of pain less than 24 hours, migration of pain to RLQ, and anorexia were not. Abdominal rigidity was again not recorded. CT scan of the abdomen was obtained, and preliminary reading was questionable for appendicitis bpericecal inflammation with inflammation at the base of appendix, with normal appendix tip, ? proximal appendicitis.Q At 7 pm, the surgery attending note stated binflammation pericecal but normal distal appendix and not thick. Plan antibiotics and observe.Q The patient continued with pain the next day and was taken to the OR for laparoscopy, where a normal appendix was removed, but a partial infarcted appendix epiploica was resected.

• • 1. Case 7

A 12-year-old boy presented to the ED at 10:40 pm complaining of abdominal pain and vomiting. Four of the 6 clinical criteria were present, but abdominal rigidity and anorexia were not present. The CT was performed at 3:10 am The preliminary reading was bsuspicious for early appen- dicitis.Q The patient was taken to the OR, where mesenteric adenitis was noted, but the appendix was normal. The official report reads bthickened tubular structure medial to cecum measuring 6 to 7 mm that might be related to the appendix,

and if indeed this is the appendix that is thickened, it is suspicious for early appendicitis, correlated clinically.Q

• • 1. Case 8

A 6-year-old girl presented to the ED at 10:42 pm with diffuse abdominal pain. She had 4 of the 6 clinical criteria, with abdominal rigidity and anorexia not recorded. A CT scan was obtained, and the preliminary CT reading was bRuptured appendicitis.Q The patient was taken to the OR, where a normal appendix was removed and bprominent lymphoid tissue and mesenteric adenopathyQ were noted by pathology. The final CT report reads bsomewhat prominent, mildly thick-walled, 7-mm-diameter appendix with no surrounding soft tissue change or fluid collection.Q

Discussion

Appendicitis, although common, is a difficult clinical diagnosis, and the consequences of missed appendicitis can be devastating. This combination of factors has led to seemingly high rates of negative appendectomy. The advent of CT scan as a highly sensitive and specific test for appendicitis has fueled debate over the use of CT to potentially decrease the rate of negative appendectomies, but no consensus has been reached regarding the role of CT scan in managing suspected appendicitis. With no existing clinical guidelines for when to use CT, Paulson et al [22] proposed clinical criteria that, if present, would allow the clinician to proceed to the OR without a CT scan. The relevant clinical question is bConsidering the utility of CT scan for suspected appendicitis, are any cases sufficiently straightforward enough not to use CT scan?Q In other words, CT scan has been advocated for use in equivocal cases, but with the historical inaccuracy of our clinical criteria and the accuracy of CT, there may be no longer be any bunequivocalQ cases of appendicitis that should go to the OR without a CT scan.

By looking at negative appendectomies, we examine the pitfalls that can lead to a negative appendectomy. In terms of the clinical criteria, it is interesting to note that 4 or more criteria were present in 5 of 8 cases, indicating that further testing is probably warranted if 4 or less criteria are present. We cannot comment on 5 or more criteria, as they were present in only 1 case. We did note that abdominal rigidity was recorded as present or absent in only 2 of 8 charts and, as such, is probably not being used enough at the study site to include in a decision-making pathway. There were also 12 cases that went directly to the OR without CT scans, which were positive for appendicitis. It would be useful to examine these cases to see if they consistently had more criteria present than the negative cases.

We noted that all cases of negative appendectomy in our series were in patients younger than 39 years, with 6 of 8 younger than 20 years and 2 of 8 younger than 7 years. There are no elderly patients in our series, perhaps because, in those patients, the differential diagnosis of abdominal

pain is broader, and they may be more likely to have a CT scan performed.

Our data indicate that, at an institution where CT scan is used liberally in the workup of suspected appendicitis (87% of appendectomies had prior CT), a low negative appendectomy rate can be achieved, 6.6%. We cannot demonstrate from this study that this use of CT is causative for the low rate. It is interesting to note, however, that whereas patients having CT had a 3.5% negative appen- dectomy rate, those with no CT had a 25% rate, a statistically significant difference. The bno-CT groupQ accounted for only 13% of all appendectomies, but 50% of the negative appendectomies.

Despite these results, one must not rely solely on the results of CT scanning. Of the 4 negative appendectomies that had preoperative CT, one was nondiagnostic, one was questionable, and two had initial reports that were mislead- ing and probably contributed to the negative appendectomy. There were also 2 cases of false-negative CT scans. The use of CT in suspected appendicitis is clearly no panacea, but appears to be a useful tool for obtaining a low negative appendectomy rate if used routinely.

Study limitations and future questions

As a retrospective study, ours has all of the limitations inherent to such studies. We were unable to control which patients underwent CT. Ideally, one would look at all cases of suspected appendicitis in a prospective manner, deter- mine the number of criteria present on a predetermined check list, and make a decision based on this, then obtain CT in all cases and determine if the results of CT would have changED management.

Conclusions

The presence of 4 of the 6 clinical criteria studied (short duration of pain [b24 hours], abdominal rigidity, migration of pain to RLQ, pain centered in RLQ, RLQ tenderness, and anorexia) is probably not sufficient to forgo preoperative CT. The majority of patients with negative appendectomies were younger than 20 years. Patients receiving a CT scan had a significantly lower chance of having a negative appendectomy than those who did not, but CT results can sometimes be inadequate or misleading and must be used in conjunction with clinical suspicion.

Acknowledgments

The authors thank Christine Hawkins and Marikay Kameczura, Medical Records Department, Resurrection Medical Center.

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