Pinch-an-inch test for appendicitis.

Abstract: Rebound tenderness is a widely used examination technique for patients with suspected appendicitis, but it can be quite uncomfortable. An alternative test for peritonitis is termed the "pinch-an-inch" test. This report describes two patients who presented with mild abdominal pain who subsequently were found to have appendicitis. In both patients, classic peritoneal signs were absent, but the pinch-an-inch test was positive. The experienced physician's bedside clinical examination remains the most critical component for rapidly identifying peritonitis. Although rebound tenderness is a widely used examination, it is uncomfortable and may be inaccurate. To perform the pinch-an-inch test, a fold of abdominal skin over McBurney's point is grasped and elevated away from the peritoneum. The skin is allowed to recoil back briskly against the peritoneum. If the patient has increased pain when the skin fold strikes the peritoneum, the test is positive and peritonitis probably is present.

Key Words: rebound tenderness, appendicitis, peritoneum, McBurney's point

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Rebound tenderness, a widely used physical examination test for patients with suspected appendicitis, can be quite uncomfortable for the patient. (1,2) Accordingly, some standard references no longer advise its use on patients with abdominal pain. (3,4) We recently developed an alternative test for peritonitis that in our experience produces less discomfort for patients. We colloquially termed this peritoneal sign the "pinch-an-inch" test. To the best of our knowledge, others have not described it.

Our pinch-an-inch test is essentially a form of rebound tenderness, only in reverse. To perform the test, a fold of abdominal skin over McBurney's point is grasped and elevated away from the peritoneum (see Fig. 1). The skin is then allowed to recoil back briskly against the peritoneum. If the patient has increased pain when the skin fold strikes the peritoneum, the test is positive and peritonitis is presumably present. As an added feature, if the pain seems excessive just during the initial pinch phase, the patient may have a very low pain threshold, a factor that can be taken into account when deciding if the patient has a surgical abdomen. We anecdotally have found the test to be remarkably helpful for the evaluation of appendicitis as exemplified by the following cases.

Case Reports

Case 1

A 19-year-old male presented to our emergency department complaining of nausea and vomiting that was preceded by approximately 12 hours of abdominal pain. He reported no anorexia or diarrhea, and his medical history and surgical history were negative. The patient's vital signs included a blood pressure of 125/81, pulse of 80, respiratory rate of 16, and a temperature of 97.5[degrees]F. He appeared to be in no acute distress. His abdomen was soft and nondistended, with normal active bowel sounds and without guarding. He was nontender to light palpation and only mildly tender to right lower quadrant deep palpation. The heeltap, obturator, Rovsing, and psoas signs were all absent, and the rectal examination was normal. On serial examinations by both the senior resident and the attending level surgeons and emergency medicine physicians, there was no rebound tenderness by the classic technique (gradually pressing over the right lower quadrant for about 15 seconds and then quickly withdrawing the hand with a positive test occurring when the patient reports increased pain as the hand is removed). (1,2,4) The only laboratory abnormality was a serum white blood cell count of 14,400 cells/high powered field (hpf) with a left shift. A presumptive diagnosis of gastroenteritis was made, and 2 liters of 0.9% normal saline bolus and 10 mg metoclopramide were administered intravenously.

However, because the pinch-an-inch test was positive, a contrasted CT scan of the abdomen was obtained that revealed findings of acute appendicitis. The surgery team performed an appendectomy through a standard Rocky-Davis incision, with operative and pathologic findings confirming acute nonperforated appendicitis. The patient's postoperative course was uncomplicated, and he was discharged home the following day.

Case 2

A 24-year-old male complained of the sudden onset of umbilical pain that became colicky and worsened over 6 hours, migrating to the right lower quadrant. He also complained of nausea and vomiting. His medical history and surgical history were negative. The patient's vital signs revealed a blood pressure of 132/67, pulse of 81, respiratory rate of 22, and a temperature of 97.9[degrees]F, and he appeared to be in no acute distress. His abdomen was soft and nondistended, with normal active bowel sounds. There was no guarding, and the rectal examination was normal. He was nontender to light palpation and only mildly tender to right lower quadrant deep palpation. On serial examinations by two physicians (attending emergency medicine and surgery), peritoneal signs were absent. Specifically, there was no rebound tenderness by the classic technique. (4) The remainder of the physical examination was unremarkable. The only laboratory abnormality was a serum white blood cell count of 13,100 cells/hpf. However, because the pinch-an-inch test was positive, a noncontrasted CT scan of the abdomen was obtained that was negative for appendicitis (see Fig. 2a). The patient was admitted for serial evaluations. Four hours later, his pain worsened and his white blood cell count rose to 20,000 cells/hpf. A repeat CT scan with contrast then revealed acute appendicitis (see Fig. 2b). Operative findings subsequently confirmed acute non-perforated appendicitis. The patient's postoperative course was likewise uncomplicated.

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Discussion

Delayed treatment of acute appendicitis can lead to significant morbidity. (5,6) However, despite recent technological advances in radiological imaging, the prompt diagnosis of acute appendicitis can be difficult. Indeed, some experts believe that overreliance on imaging at the expense of the bedside examination may actually increase appendicitis-related morbidity. (7,8) Arguably, both of these patients might have been better served by undergoing surgery directly, without the delay of CT imaging. The experienced physician's bedside clinical examination remains the most critical component for rapidly identifying those patients with surgical disease. (7,8) Although rebound tenderness is a widely used examination technique for detecting peritonitis, (1,2,9) it is quite uncomfortable and can be inaccurate, despite serial examinations. (10,11) Therefore, research efforts should be directed toward developing and validating improved bedside assessments of peritonitis.

To illustrate the difference between our pinch-an-inch test and classic rebound tenderness, consider the difference between putting a golf ball (ie, classic rebound) and dropping a golf ball (ie, pinch-an-inch). With classic rebound, an examiner may find it difficult to apply a consistent amount of pressure over serial examinations or between multiple examiners. Likewise, it is challenging to quickly release the examining hand upward without first applying at least some brief downward pressure (similar to putting without any backstroke). In that case, is the examiner really assessing the rebound of the peritoneum upward against the skin, or the slight, initial downward push? In contrast, the initial force applied of the pinch-an-inch appears to be more objective (see Fig. 1), and releasing the pinch simply allows the built up elastic recoil to occur (like dropping a golf ball from the same height repeatedly). One important caveat to clinicians is the fact that patients with appendicitis may actually have hyperesthesia over McBurney's point, and an excessive pain response to the "pinch" phase should not be dismissed out of hand. (12)

[FIGURE 2 OMITTED]

Conclusion

We hope that our pinch-an-inch examination technique may eventually offer a more comfortable and accurate alternative to classic rebound tenderness. Toward this effort, we will conduct a prospective study to evaluate its accuracy and relative comfort in diagnosing appendicitis.

References

1. Wolfe JM, Henneman PL. Acute Appendicitis. In: Marx JA, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. St. Louis, Mosby, 2002, 5th ed., p 1294.

2. Jones RS. Acute Abdomen. In: Townsend CM, ed. Sabiston Textbook of Surgery. Philadelphia, WB Saunders, 2001, 16th ed., pp 802-814.

3. Matthews JB, Hodin RA. Acute Abdomen and Appendix. In: Greenfield LJ, ed. Surgery: Scientific Principles and Practice. Philadelphia, Lippincott Williams & Wilkins, 2001, 3rd ed.

4. Silen W. Cope's Early Diagnosis of the Acute Abdomen. Oxford, Oxford University Press, 2000, 20th ed.

5. Von Titte SN, McCabe CJ, Ottinger LW. Delayed appendectomy for appendicitis: causes and consequences. Am J Emerg Med 1996;14:620-622.

6. Cappendijk VC, Hazebroek FW. The impact of diagnostic delay on the course of acute appendicitis. Arch Dis Child 2000;83:64-66.

7. Lee SL, Walsh AJ, Ho HS. Computed tomography and ultrasonography do not improve and may delay the diagnosis and treatment of acute appendicitis. Arch Surg 2001;136:556-562.

8. Flum DR, Morris A, Koepsell T, et al. Has misdiagnosis of appendicitis decreased over time? A population-based analysis. JAMA 2001;286:1748-1753.

9. Wagner JM, McKinney WP, Carpenter JL. Does this patient have appendicitis? JAMA 1996;276:1589-1594.

10. Liddington MI, Thomson WH. Rebound tenderness test. Br J Surg 1991;78:795-796.

11. Alshehri MY, Ibrahim A, Abuaisha N, et al. Value of rebound tenderness in acute appendicitis. East Afr Med J 1995;72:504-506.

12. Old JL, Dusing RW, Yap W, et al. Imaging for suspected appendicitis. Am Fam Physician Jan 1 2005;71:71-78.

LTC Bruce D. Adams, MD, FACEP, CAPT Devin Rickett, MD, CAPT Philip A. Albaneze, MD, CAPT Michael D. Jones, MD, and MAJ Gerald York II, MD

From the Department of Emergency Medicine, Brooke Army Medical Center, San Antonio, TX.

Reprint requests to LTC Bruce D. Adams, Chief of Emergency Medical Services, Department of Emergency Medicine, Brooke Army Medical Center, San Antonio, TX 78234. Email: [e-mail]

There are no financial conflicts or outside sources of financial support to disclose. There are no proprietary interests involved in this study.

Institutional Review Board approval has been received for this project.

Accepted August 25, 2005.

RELATED ARTICLE: Key Points

* The experienced physician's bedside clinical examination remains the most critical component for rapidly identifying appendicitis.

* Rebound tenderness is a widely used examination, but it is uncomfortable and may be inaccurate.

* Through two case reports, a new examination technique termed "pinch-an-inch" is introduced.

* A fold of abdominal skin over McBurney's point is grasped and elevated away from the peritoneum. The skin is then allowed to recoil back briskly against the peritoneum. If the patient has increased pain when the skin fold strikes the peritoneum, the test is positive and peritonitis is presumably present.