DOI:10.2214/AJR.07.2917
AJR 2008; 190:707-711
© American Roentgen Ray Society
Dropped Appendicolith: CT Findings and Implications for Management
Ajay K. Singh1,2,
Peter F. Hahn2,
Debra Gervais2,
Gopal Vijayraghavan1 and
Peter R. Mueller2
1 Department of Radiology, University of Massachusetts Memorial Medical Center,
Worcester, MA.
2 Division of Abdominal Imaging and Interventional Radiology, Department of
Radiology, Massachusetts General Hospital, 55 Fruit St., Boston, MA
02114.
Received July 23, 2007;
accepted after revision September 25, 2007.
Address correspondence to A. K. Singh.
Abstract
OBJECTIVE. The aim of this study was to discern the CT features of
appendicoliths retained after appendectomy and evaluate the management
options.
CONCLUSION. Retained, or dropped, appendicolith most often presents
as an area of high attenuation less than 1 cm in diameter with an associated
abscess close to the cecum or Morison's pouch. CT-guided drainage can be used
to manage abscesses associated with dropped appendicolith in selected
cases.
Keywords: abscess • appendectomy • dropped appendicolith
Introduction
Appendicitis is a common surgical emergency, affecting nearly 7% of the
population in a lifetime. Laparoscopic appendectomy is widely gaining
acceptance as the treatment of choice of patients with acute appendicitis and
is advocated by the European Association for Laparoscopic Surgery even for
perforated appendicitis [1].
Although compared with open surgery, laparoscopic appendectomy is associated
with less pain, shorter hospital stay, lower incidence of wound infection, and
earlier return to full activity, laparoscopic appendectomy is complicated by
postoperative abscess approximately five times more frequently than is open
surgery
[2–4].
Retained, or dropped, appendicolith is a rare complication that can occur
as a consequence of stone expulsion from the appendix before or during
appendectomy. The appendicolith can be a nidus for future intraabdominal
abscess formation; therefore, recognition of its presence is of great clinical
significance in the care of patients with postappendectomy abscesses. Like
dropped gallstones, appendicoliths are known to be retained after
appendectomy, but the literature on dropped appendicoliths is limited mainly
to case reports. The limited knowledge on this subject can be quantified by
the existence of fewer than 30 cases of dropped appendicolith in the
literature over the last 40 years
[5–16];
fewer than 10 reports describe the imaging findings. We describe the CT
features of appendicoliths retained after appendectomy and evaluate the
management options in the largest, to our knowledge, reported case series of
dropped appendicolith in the radiologic and surgical literature.
Materials and Methods
The local institutional review board approved this study, which was
conducted in accordance with the HIPAA. Because it was a retrospective study,
the institutional review board waived the requirement that informed consent be
obtained from patients. We searched our radiologic database for the cases of
all patients who had undergone appendectomy from July 1997 to July 2007 and in
which the primary contrast-enhanced CT diagnosis was dropped appendicolith.
The inclusion criteria were a history of appendectomy; presence of a calcific
area of high attenuation outside the cecum on postappendectomy CT; and
findings on CT before appendectomy of an appendicolith in the inflamed
appendix similar in configuration to the calcification on postoperative CT or
an operative report of a repeated surgical procedure confirming the diagnosis
of dropped appendicolith. Patients with history of appendectomy in which the
right lower quadrant area of high attenuation could not be unambiguously
localized outside the lumen of the cecum were excluded from the study. This
step was taken to exclude cases in which retained barium or fecalith could
mimic a retained appendicolith. None of the patients who satisfied the three
inclusion criteria (n = 11) met the exclusion criteria.
The mode of surgery (laparoscopic vs open), duration between appendectomy
and presen tation, pathology notes, and final outcome were documented. In each
case, the available length of follow-up after therapy for retained
appendicolith was recorded. Catheter drainage of abscesses was considered
successful when the procedure resulted in resolution of the abscess without
surgery.
CT Technique
The contrast-enhanced CT examinations were performed with a helical CT
scanner. Ten patients underwent IV and oral contrast-enhanced CT after
appendectomy. One patient underwent CT after appendectomy with oral but not IV
contrast administration. The contrast-enhanced CT scans were obtained after
injection of 90–140 mL of nonionic contrast material (300–370 mg
I/mL) at 2–3 mL/s. Eight patients underwent CT before appendectomy with
IV and either rectal or oral contrast administration. The CT slice thickness
for the abdominal and pelvic scans was 5 mm, and the pitch was 1.5. The images
were available for interpretation on a PACS workstation (Impax DS3000 AGFA
SP4SU2, AGFA Technical Imaging Systems).
CT Evaluation
Two board-certified radiologists in consensus evaluated all 10 CT scans. In
case of lack of consensus between the two radiologists, a third radiologist
was involved in the final CT interpretation.
CT Findings
The preoperative and postoperative CT scans were evaluated for size and
number of appendicoliths and abscesses. The indication for postoperative CT
was documented, and the CT findings of retained appendicolith were compared
with those on preoperative CT. When available, the preoperative CT scans were
reviewed by two board-certified radiologists to confirm radiologic evidence of
acute appendicitis.
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Fig. 1 —9-year-old girl with dropped appendicolith after open
appendectomy for suppurative appendicitis. Contrast-enhanced CT scan obtained
10 days after appendectomy shows abscess (arrowhead) containing
appendicolith (arrow). Abscess was drained under sonographic
guidance, but attempts at retrieval of appendicolith with snare failed.
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Results
Eleven patients (seven male, four female; mean age, 31.4 years; range,
9–67 years) presented with postappendectomy appendicolith 7
days–20 months (mean, 2.5 months; median, 15.5 days) after appendectomy.
Seven of the 11 patients had undergone laparoscopic appendectomy; one,
conversion of laparoscopic to open appendectomy; and three, primary open
appendectomy.
Clinical Presentation After Appendectomy
Eight patients presented with clinical signs of focal pain, fever, elevated
WBC count, or a combination of these findings. The indication for CT for these
eight patients correlated well with the CT findings. For three patients,
dropped appendicolith was diagnosed when CT was performed for the following
unrelated reasons: staging of ampullary carcinoma, right upper quadrant pain
from acute cholecystitis, and epigastric pain from gastritis. Two of these
three patients had no abscess associated with the appendicolith, but the third
patient had a 2.5 x 1.5 cm abscess. Overall, in three patients, a
dropped appendicolith was incidentally diagnosed on CT, and in eight patients
the appendicolith actively caused symptoms that led to the CT examination. In
the patient with a history of cholecystectomy, the diagnosis of dropped
appendicolith was confirmed by comparison of the preoperative CT scans, which
showed an appendicolith, with the postappendectomy CT scans. Leukocytosis was
present in nine of the 11 patients with retained appendicolith, and all of
these patients had an abscess detectable on CT. The mean WBC count in the nine
patients in whom it was elevated was 13.2 x 109/L (range,
11–16.3 x 109/L).
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Fig. 2 —42-year-old man with dropped appendicolith after open
appendectomy. Contrast-enhanced CT scan obtained 14 days after surgery because
of increasing right lower quadrant pain and elevated WBC count shows right
lower quadrant abscess (arrow) with calcified appendicolith
(arrowhead). Surgical drainage was performed, and patient made full
recovery.
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CT Findings
The dropped appendicoliths were located in the paracecal region (n
= 9) and Morison's pouch (n = 2). An abscess was associated with the
dropped appendicolith in nine patients, and in two patients the dropped
appendicolith had no associated abscess. The appendicoliths were in Morison's
pouch in two patients, caudal to the cecum in three patients, and medial to
the cecum in three patients. In the other three patients, the appendicoliths
were anterior (deep in relation to the rectus abdominis muscle), lateral, and
posterior to the cecum (Figs.
1,
2,
3A,
3B,
3C). In the nine patients who
had abscesses associated with dropped appendicolith, the abscess cavities were
2–6 cm in diameter, and all contained a high-attenuation
(105–1,000 H) focus measuring 4–10 mm in diameter. The
preoperative CT images of eight patients were available and reviewed by the
two radiologists to confirm radiologic evidence of acute appendicitis. The CT
scans of all eight of these patients showed an appendicolith with the
additional findings of appendiceal perforation in two patients and
periappendicular abscess in another two patients.
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Fig. 3A —34-year-old woman with dropped appendicolith in Morison's
pouch. Contrast-enhanced CT scan obtained 7 days after appendectomy shows
Morison's pouch abscess containing appendicolith (arrowhead).
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Fig. 3C —34-year-old woman with dropped appendicolith in Morison's
pouch. Follow-up CT scan after successful drainage of abscess shows faintly
visible persistent appendicolith (arrowhead) in Morison's pouch.
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Treatment
The treatment of the 11 patients included primary surgery (n = 2),
surgery after failed catheter drainage (n = 2), successful catheter
drainage (n = 4) (Fig.
4A,
4B,
4C), and conservative
management (n = 3). One of the four patients who underwent successful
catheter drainage also underwent successful percutaneous CT-guided basket
extraction of an appendicolith. Six of the 11 patients had been referred to
the interventional radiologist for percutaneous catheter drainage. In two
cases, the abscess did not resolve with catheter drainage, and the patients
needed surgical removal of the appendicolith. In one patient, the cause of
failure was retention of a 5.8-cm-long segment of appendix after the first
operation and dislodgement of a catheter after 28 days of drainage. In the
second patient, a Morison's pouch abscess had a large phlegmonous component
that prevented adequate catheter drainage. In four patients, percutaneous
catheter drainage was successful. Postdrainage CT showed persistence of the
appendicolith in three of these patients with resolution of the abscess and
the symptoms. In the fourth patient, percutaneous extraction of the
appendicolith was successful. All patients in whom catheter drainage was
successful had a well-defined liquefied abscess. One of the six patients who
underwent catheter drainage at an outside facility and needed a second
catheter drainage procedure to manage the abscess later developed partial
small-bowel obstruction. In three patients in whom the appendicolith was
incidentally diagnosed on CT performed for an unrelated indication (ampullary
carcinoma staging, suspected cholecystitis, and gastritis), a conservative
approach was successful.
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Fig. 4A —24-year-old man with retained appendicolith managed with
percutaneous retrieval. Axial contrast-enhanced CT scan after appendectomy
shows abscess containing appendicolith (arrow) in right lower
quadrant.
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Fig. 4B —24-year-old man with retained appendicolith managed with
percutaneous retrieval. Axial CT scan shows 22-mm-diameter Wittich nitinol
stone basket (arrow) passed through 12-French sheath to retrieve
appendicolith.
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Fig. 4C —24-year-old man with retained appendicolith managed with
percutaneous retrieval. Photograph shows Wittich nitinol stone basket
(curved arrow) and retrieved appendicolith (straight
arrow).
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The CT-guided drainage procedures on the six patients were directed at the
abscess rather than the appendicolith. However, percutaneous appendicolith
extraction was attempted in two patients who underwent catheter drainage and
was successful in one patient. In one pediatric patient, percutaneous
retrieval of a dropped appendicolith was attempted but was not successful.
This patient was successfully treated with percutaneous catheter drainage.
Extraction of an appendicolith in a 24-year-old man was successful with a
Wittich nitinol stone basket (WNSB-12–24, Cook) passed through a
12-French sheath (Fig. 4A,
4B,
4C). This patient recovered
rapidly from a 6-cm-diameter postappendectomy abscess and was discharged 2
days after the procedure.
Discussion
As with cholecystectomy in which a gallstone is inadvertently retained,
appendicoliths can be left behind after appendectomy for acute appendicitis.
These appendicoliths are retained because of extrusion from a perforated
appendix before surgery or owing to failure to recognize and extract an
appendicolith during surgery. There can be a latency of days to years between
appendectomy and clinical manifestation of a dropped appendicolith. These
retained appendicoliths can manifest as abscess formation or, less commonly,
as fistula formation and a nonhealing wound after appendectomy.
The typical imaging description of symptomatic dropped appendicolith is an
abscess containing one or more high-attenuation foci, most commonly in the
pelvis or Morison's pouch. In rare instances, the appendicolith has localized
in the iliopsoas compartment or the gluteal region
[15]. In making the diagnosis
of dropped appendicolith, we found it valuable to compare postoperative CT and
preoperative CT scans. In doubtful cases, the lack of an appendicolith on
preoperative CT scans should reduce suspicion of a dropped appendicolith,
increasing the probability that a high-attenuation focus is instead retained
oral contrast material or a surgical clip. Other causes of calcific areas of
high attenuation in the abdomen include dropped gallstones, calcified epiploic
appendagitis, dropped surgical clips, and calcified mesenteric lymph nodes.
Among the reported causes of calcific areas of high attenuation in the
abdomen, dropped appendicolith is much less common than dropped gallstones,
which have been reported to spill out of the gallbladder in as many as 40% of
cholecystectomies.
The management of symptomatic dropped appendicolith most commonly described
in the literature is open or laparoscopic surgery with abscess drainage and
extraction of the calculus. Percutaneous removal of dropped appendicolith with
balloon catheters passed through the dilated sinus has been described in a
case report [16]. In one
patient, we successfully performed percutaneous retrieval of an appendicolith
using a stone basket passed through a 12-French sheath. Although open surgical
incision and drainage with retrieval of the appendicolith is the preferred
method of treatment, in the coming years, percutaneous retrieval may gain
greater acceptance.
All eight cases of dropped appendicolith described since 2004
[5,
10,
12,
15] have been secondary to
laparoscopic appendectomy. Our findings were in agreement that most cases of
dropped appendicolith occur during laparoscopic rather than open appendectomy.
In our study, eight of the 11 appendectomies were initially attempted by
laparoscopic means. One patient needed the operation converted to open
appendectomy because of the presence of dense inflammatory adhesions. In our
series, the interval between surgery and postappendectomy CT varied from 7
days to 20 months (mean, 2.5 months). This interval is in agreement with
reports in the literature, in which the time between appendectomy and the
diagnosis of dropped appendicolith varies from 10 days to several years
[5–16].
Like those of dropped gallstones, the locations of abscesses and
appendicoliths in our cases were limited to the right side of the abdomen,
either Morison's pouch or the paracecal region. In theory, an appendicolith
can lodge elsewhere in the abdominal cavity. Even a subcutaneous location has
been described in the literature
[7].
In four of our six patients who underwent the procedure, catheter drainage
of an abscess was successful. Because of its relatively less invasive nature
and the potential for success, catheter drainage can be used as an alternative
initial approach. A study by Buckley et al.
[15] did not show value of
percutaneous drainage in the management of dropped appendicolith, but our
experience suggests that a trial with image-guided percutaneous catheter
drainage may be beneficial before the decision is made to proceed with
operative retrieval of an appendicolith.
The study was limited because we included only patients whose CT findings
showed a dropped appendicolith. It is conceivable that a number of
asymptomatic dropped appendicoliths were not included in the study because the
radiologist reading the CT scans did not mention an appendicolith in the
report. The small number of cases also limited the study of percutaneous
drainage.
Dropped appendicoliths after laparoscopic appendectomy are rare, but
awareness of the CT findings on the part of the radiologist can be helpful for
prompt diagnosis and management of this potential source of intraperitoneal
infection. Retained appendicoliths can cause abscess formation after surgery
and can be a source of persistent infection. A trial of image-guided catheter
drainage with or without percutaneous stone extraction may be beneficial in
avoiding repeated surgery.
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Abstract
Introduction
