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Breast Imaging |
1 From the Departments of Radiology (D.U., R.A.C.) and Gynecology and Obstetrics (M.K.G.N.), Karolinska Institute at Danderyds Hospital, S182 88 Danderyd, Sweden. From the 2002 RSNA scientific assembly. Received April 12, 2003; revision requested July 1; revision received December 12; accepted January 30, 2004. Address correspondence to D.U. (e-mail: dieter @swipnet.se).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: One hundred eight consecutive lactating women who were clinically suspected of having a breast abscess were examined with US. Abscesses depicted at US were treated with US guidance, and the success of US-guided treatment was retrospectively determined.
RESULTS: Fifty-six abscesses were identified at US in 43 women; all abscesses were treated with US guidance: 23 with needle aspiration and 33 with catheter drainage. Treatment method was determined according to the size of the abscess. Abscesses that were smaller than 3 cm in maximum diameter were treated with needle aspiration, and abscesses that were 3 cm or larger in maximum diameter were treated with catheter insertion. One patient who was treated with needle aspiration subsequently underwent surgical intervention; all others were successfully treated with US intervention. Catheter placement was well tolerated (mean pain score 2.3 in 22 women by using a subjective pain scale of 0–10).
CONCLUSION: US-guided needle aspiration of abscesses smaller than 3 cm and US-guided catheter drainage of abscesses 3 cm or larger are successful means of treating breast abscesses.
© RSNA, 2004
Index terms: Abscess, percutaneous drainage, 00.1262 • Breast, abscess, 00.212 • Breast, lactation, 00.54 • Breast, US, 00.1298, 00.12983 • Ultrasound (US), guidance, 00.12985, 00.12986
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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Our institutional review board did not require approval or informed consent for this retrospective study. However, we nevertheless obtained informed consent from every patient for the procedures.
Imaging and Interpretation
Each breast US examination and therapeutic procedure was performed by one of five radiologists (D.U., 12 years experience) who subspecialize in breast imaging and who have 10–12 years experience with breast US and intervention. Various types of commercially available US equipment with 7.5–12-MHz probes were used. Color Doppler US imaging was also routinely performed, except in some cases early in the series.
A sonographic diagnosis of mastitis was made when one or more of the following signs were present: area(s) of decreased parenchymal echogenicity or increased fat echogenicity, skin thickening, increased vascularity on color Doppler images, reactive or enlarged axillary lymph nodes, and/or dilated lymphatics.
A sonographic diagnosis of abscess was made when a round, oval, or irregularly shaped hypoechoic lesion (homogeneous or inhomogeneous) was present and showed at least some acoustic enhancement within which no vessels were observed at color Doppler US.
Abscess Treatment
If a lesion consistent with abscess was found, US-guided needle puncture was performed by using a 21-gauge needle to confirm the diagnosis and to subjectively determine the viscosity of the fluid. If the needle puncture findings confirmed the presence of an abscess, some of the aspirated material was sent for culture, and US-guided treatment was immediately performed.
On the basis of the experience reported by Karstrup et al (8,9), we decided to treat abscesses that were smaller than 3 cm in maximum diameter with aspiration alone. Abscesses that were 3 cm or larger in maximum diameter were treated with the insertion of a Cook HPD catheter (Cook Europe, Bjaeverskov, Denmark). All US-guided procedures were performed by using a freehand technique.
US-guided aspiration for abscesses with a maximum diameter that was smaller than 3 cm consisted of placing a 21-, 19-, 16-, or 14-gauge needle or a 1.7–2.0-mm plastic cannula and flushing two or three times with sterile saline. The size of the needle or cannula that was used depended on the viscosity of the pus that was found at the diagnostic needle puncture. Larger needles or cannulas were used when subjectively more-viscous pus was present. After the initial aspiration and flushing, the patient returned for follow-up US 2 or 3 days later. If the abscess cavity was sonographically visible at follow-up, the cavity was reaspirated and flushed. Follow-up visits continued at increasing intervals (up to 5 days between visits) until the abscess was no longer visible at US, and the patient was asymptomatic.
For abscesses with a maximum diameter of 3 cm and larger, local anesthetic was administered to the patients and a nick was made in the skin to facilitate catheter insertion. Catheter placement was performed by using the trocar technique. The size of catheter that was used varied from 6 to 8 F, with the larger diameter catheters being used when more viscous pus was found at diagnostic needle puncture. After catheter placement, the abscess was completely aspirated and then irrigated three to five times with sterile saline until the aspirate was clear. Early in this series, the catheter was stitched to the skin; after the first several patients, however, lockable catheters (Navarre; Bard, Covington, Ga) were used. The abscess was irrigated with sterile saline three to four times daily by the patient, a relative, or an individual at a health care institution. Follow-up US was performed 2–3 days after catheter insertion, and the cavity was irrigated with sterile saline, as described above. Additional follow-up examinations were performed at increasing intervals (depending on the condition of the patient) until the patient was asymptomatic and the abscess cavity was no longer visible at US. The catheter was removed when minimal (<4 mL) or no saline could be instilled through the catheter for flushing, and the abscess was no longer visible at US.
When local anesthesia was not sufficient to control pain, an analgesic that produces systemic effects, usually pethidine hydrochloride (50 mg administered intramuscularly) (Petidin Ipex; Meda, 170 09 Solna, Sweden) was administered. The catheter was always inserted through uninvolved tissue to minimize the possibility of leakage of milk, pus, or saline around the catheter. The catheter was also placed away from the nipple to avoid interfering with continued breast-feeding. On occasion, insertion of the catheter required considerable pressure because normal parenchyma can be very firm.
After undergoing US-guided needle aspiration or catheter placement, all patients were treated with penicillinase-resistant antibiotics, usually 500 mg of floxacillin administered orally three times a day for at least 10 days.
Follow-up
Immediately after US-guided catheter placement, the subjective perception of pain related to the procedure was assessed by using a visual analog scale that measures pain from zero (none) to 10 (severe), as is described by Scott and Huskisson (18)
Long-term cosmetic results were analyzed by means of a follow-up questionnaire, which was mailed to all women treated for abscess. The questionnaire asked the patients whether there was any residual scarring related to treatment, and, if so, whether the scar was cosmetically disturbing.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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In the 43 women who had US evidence of one or more abscesses, a total of 56 abscesses were found. All of these abscesses were confirmed with findings from US-guided needle puncture. Thirty-four (79%) of these 43 women had one abscess each, six (14%) had two abscesses each, two (5%) had three abscesses each, and one (2%) had four abscesses. Seven of the 43 women (16%) had more than one abscess (range, 2–4) in one breast (Table 1). Four patients had bilateral abscesses. Of these four patients, two had one abscess in the left breast and one abscess in the right breast. The other two patients had one abscess in the right breast and two abscesses in the left breast.
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Of the 56 total abscesses, only five abscesses had homogeneous internal echotexture, whereas 51 were inhomogeneous and had echogenic areas. Twenty-nine of the abscesses were oval, 11 were round, and 16 were irregular in shape, sometimes with long, fingerlike components. Four of the 16 irregularly shaped abscesses were ill defined and surrounded by highly vascular tissue, as observed on color Doppler US images. Twenty-four of the oval and nine of the round abscesses were slightly or moderately lobulated (Figs 1, 2). Superficial abscesses usually had associated skin thickening and, occasionally, subcutaneous dilated lymphatics.
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Twenty-three of the 56 abscesses, occurring in 14 patients, were treated with US-guided needle aspiration and flushing with sterile saline. The mean maximum diameter of the abscesses treated with needle aspiration was 2.2 cm (range, 1–4 cm). One very irregular abscess, which had fingerlike extensions and a maximum diameter of 4 cm, was treated with aspiration alone at the patient’s request; all other abscesses that were treated with needle aspiration alone were less than 3 cm maximum diameter. At follow-up, repeat needle aspirations were required in 12 of these 23 abscesses (52%). The total number of additional aspirations ranged from one to five; the mean number of aspirations was 1.8. One patient’s surgeon decided to perform surgical incision and drainage instead of having her return for repeat needle aspiration; US-guided aspiration was successful in treating the remaining 22 abscesses.
Thirty-three of the 56 abscesses, occurring in 29 women, were treated with US-guided catheter placement. Five of these 29 patients (17%) were also given an analgesic that produces systemic effects to control pain. The mean maximum diameter of the 33 catheter-treated abscesses was 5.2 cm (range, 3–10 cm). It was not necessary to place more than one catheter for the drainage of any abscess. The catheter was left in place an average of 6.4 days (range, 1–25 days). Five of these 33 abscesses (15%) recurred following catheter removal. All recurrences, however, were successfully treated with US guidance, one with catheter reinsertion and four with needle aspiration. In 11 cases, milky fluid was observed at flushing. This was particularly true for larger abscesses. Ten patients who were treated with catheter placement were hospitalized during treatment because of poor clinical condition; mean hospital stay was 5 days (range, 2–9 days). No patient treated with catheter placement required surgical intervention.
Of the 29 women who were treated with catheter drainage and whose medical records were available for retrospective review, 17 continued breast-feeding throughout treatment. Ten were given medication (typically bromocriptine or cabergoline) to stop lactation during treatment of the abscess, and one patient had already stopped breast-feeding.
Subjective pain perception was measured in 22 of the 29 patients who were treated with US-guided catheter placement. Seven patients were inadvertently not assessed for pain perception. On the visual analog scale, which is described by Scott and Huskisson (18) and measures pain from 0 (none) to 10 (severe), the subjective pain related to catheter insertion averaged 2.3 (range, 0.5–6.5).
At 38–63 months after treatment, a questionnaire inquiring about satisfaction with cosmetic result was sent to all 43 women with abscesses. Thirty-seven of 43 women (86%) replied; of the 37 responders, 35 (94%) were satisfied with the cosmetic result, whereas two women were not. These two women did not state the reason they were dissatisfied, and because the questionnaire was anonymous, we were unable to follow up with these patients.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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The most common causative organism of lactation-related mastitis and abscess is S aureus. Because the organism is usually ß-lactamase producing, penicillinase-resistant antibiotics should be used. The organism probably gains entry into the breast tissue through a duct or a fissure on the nipple (1,21,23).
The incidence of mastitis following delivery also depends on the frequency of breast-feeding; in our geographic area, breast-feeding is very high, with nearly 95% of mothers breast-feeding at the time their infants are 2 months old (24).
This study does not determine the overall prevalence of breast abscesses among lactating women or among lactating women with mastitis, since only those women clinically suspected of having an abscess as a complication of mastitis were referred for US. This is probably why abscesses were found in 40% of the women in this study. Many lactating women were treated for mastitis during this study, but they were not clinically suspected of having an abscess. These women were not referred for US; therefore, they were not included in this study.
US is very useful in the detection of breast abscesses that are caused by complications of mastitis. Clinical assessment can be limited by breast tenderness, and an abscess deep within the breast (or in a large breast) may be difficult to detect clinically. Therefore, whenever there is clinical suspicion that an abscess might be present, or if mastitis does not promptly respond to appropriate therapy, US should be performed. US can also rule out the presence of an abscess and thus prevent unnecessary intervention (3).
Color Doppler US images can be helpful by depicting increased vascularity within inflamed hypoechoic tissue that might otherwise be mistaken for an abscess at US. Patients with severe mastitis should be periodically assessed with US until clinical symptoms have resolved. Periodic assessment can help to detect the development of an abscess at an early stage.
We believe mammography should not be performed in diagnosing acute abscess in lactating women because mammography may be difficult to perform because of pain. Likewise, changes that are caused by inflammation may result in increased radiographic density, which can mask focal lesions (4,5). However, if the patient does not promptly respond to appropriate therapy, then we believe mammography should be performed to look for signs of a possible underlying malignancy.
The conventional treatment of a breast abscess has been surgical incision and drainage (1,2). In recent years, however, various authors have described successful percutaneous treatment of breast abscesses by using US guidance (6–13) or even palpatory guidance (25). Because breast abscesses are relatively rare and because US-guided treatment is a relatively recent development, there are no large studies, to the best of our knowledge, that describe results of US-guided treatment of these abscesses in lactating women.
We decided at the outset to limit this study to lactating women because abscesses in nonlactating women tend to be more heterogeneous in terms of causative organisms (7,10,26). For instance, a subset of nonpuerperal abscesses in patients with mammary duct–associated inflammatory disease sequence requires the surgical excision of major ducts to prevent fistulas and recurrence (27). In our experience, however, US findings, the interventional techniques, and the outcomes for abscesses in lactating women are similar to those in nonlactating women.
Our decision to treat abscesses with a maximum diameter of less than 3 cm by using needle aspiration and abscesses with a maximum diameter of 3 cm and larger by using catheter drainage, was based on the results reported by Karstrup et al (8,9). In our study, we were successful in treating all but one abscess by using this approach. Nonetheless, this study does not substantiate 3 cm as being the ideal cutoff point between needle aspiration and catheter drainage. It may not be necessary to place a catheter in all patients who have abscesses that are 3 cm and larger. This question is, therefore, not resolved with our findings.
To minimize pain, it is important to administer ample local anesthetic before the catheter is introduced. If a local anesthetic does not control pain, then an analgesic that produces systemic effects should be administered. Once this is administered, we believe all abscesses can be drained with minimal patient discomfort.
Among the women who chose to continue breast-feeding, there were no signs of harm to the infants, nor were there any other problems related to continuing breast-feeding. This is in accordance with previous reports (7,8,9,23).
The catheter can be removed when US shows no residual fluid accumulation, when pus no longer can be aspirated, and when only minimal saline can be irrigated into the residual cavity. In women with a catheter in place, the irrigation fluid sometimes may contain milk. We believe this is because of duct damage caused by the inflammation process. In these cases, the catheter should remain in place until milk is no longer aspirated. Sometimes it is even advantageous to stop lactation by pharmacologic intervention; otherwise, milk may accumulate in the abscess cavity. This accumulation may result in reinfection, and we consider such reinfection to be the underlying mechanism for many of the recurrent abscesses in our series. In four of five recurrent abscesses, milky fluid was observed when irrigating, but, despite this, the catheter was removed in two cases. In the two other cases of recurrence, the catheter was removed prematurely because of milk leakage along the catheter (Fig 3).
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Concerning our study limitations, we did not include nonlactating women with abscess in this study, even though we saw and successfully treated many such women during this time. Therefore, we cannot state with certainty that our results will apply to treatment of breast abscesses in nonlactating women. We chose to use a 3 cm maximum abscess cavity diameter as a cutoff point between treatment with needle aspiration versus treatment with catheter placement. Our findings, however, do not confirm if this is the optimal cutoff point. Furthermore, our findings do not indicate if it is necessary to use catheter placement for larger abscesses or if these abscesses may be successfully treated with needle aspiration alone.
During this study, 43 lactating women had a total of 56 breast abscess that were detected at US; all abscesses were treated with US guidance, and treatment was successful in all but one woman.
In conclusion, US is a useful method for facilitating the diagnosis of breast abscesses in lactating women. US-guided needle aspiration of abscesses with a maximum diameter of less than 3 cm and US-guided catheter treatment of abscesses with a maximum diameter of 3 cm and larger are safe, well-tolerated, and successful means of treating breast abscesses in lactating women.
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FOOTNOTES |
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Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, D.U.; study concepts, all authors; study design, D.U.; literature research, D.U., R.A.C.; clinical studies, D.U., M.K.G.N.; data acquisition, D.U., M.K.G.N.; data analysis/interpretation, D.U., R.A.C.; manuscript preparation, definition of intellectual content, and editing, D.U., R.A.C.; manuscript revision/review, all authors; manuscript final version approval, D.U., R.A.C.
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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  J. M. Sabate, M. Clotet, S. Torrubia, A. Gomez, R. Guerrero, P. de Las Heras, and E. Lerma Radiologic Evaluation of Breast Disorders Related to Pregnancy and Lactation RadioGraphics, October 1, 2007; 27(suppl_1): S101 - S124. [Abstract] [Full Text] [PDF]
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