The misleading appearance of silver nitrate on plain radiography

Abstract

Cauterisation with silver nitrate is commonly used to treat overgranulation. Silver nitrate has a high density and a high mass attenuation coefficient, and it is therefore highly radio-opaque. We present a case in which its topical application to an area of overgranulation was interpreted as a bony fragment by the reporting radiologist in a patient with a supracondylar humeral fracture whose radiograph after removal of K-wires showed a large radio-opaque lesion. Although not a new phenomenon, it is one not widely known, and it can lead to confusion and unnecessary further imaging. KEYWORDSSilver nitrate -Radio-opacity -Overgranulation Case HistoryWe report the case of a three-year-old girl who sustained a supracondylar humeral fracture. This was treated with closed reduction and K-wire fixation. The fracture healed well and the K-wires were removed under nitrous oxide and oxygen three weeks following the injury. On removal of the wires, considerable overgranulation tissue was noted on the medial side of the elbow, which was treated with silver nitrate.Plain radiograph of the elbow following the procedure demonstrated a 15mm  10mm radio-opaque lesion on the medial side of the elbow (Fig 1), which was interpreted by the reporting radiologists to be 'a large detached bony fragment lying in the cubital fossa'. This diagnostic misinterpretation was noticed in clinic at a follow-up visit by the treating orthopaedic surgeon and reported back to the radiology department. The history of silver nitrate application had not been documented on the radiograph request form. However, previous films were available for comparison. DiscussionThe formation of granulation tissue is a necessary part of the proliferative phase of wound healing. Dermal fibroblasts increase in number and synthesise a network of protein fibrils. Local tissue hypoxia promotes angiogenesis and this protein framework is infiltrated by capillary buds. In normal wound healing, epidermal keratinocytes proliferate at the margins of the wound before migrating across the newly formed granulation tissue. These keratinocytes form an epithelial membrane and the wound is sealed. Occasionally, the proliferative phase is excessive and granulation tissue is formed well above the height of surrounding healthy tissue. This is described as 'overgranulation'. The cause of this exuberance is not well understood but it may represent an aberrant response to a persistent inflammatory stimulus.When overgranulation occurs it impedes epithelialisation and delays wound healing. Various methods have been described to treat overgranulation including topical steroids, steroid impregnated tape and cauterisation with silver nitrate. Silver nitrate inhibits fibroblast proliferation and usually leads to a rapid resolution of the overgranulation.The mass attenuation coefficient is a standardised measure of attenuation of materials independent of their physical state. This coefficient, however, is dependent on the energy of incident radiation due to K shell effects (assumed to be ...

The Erroneous Appearance of Silver Nitrate on CT Imaging in Patients with Severe Otitis Externa; A Case Series

“…As a metal its mass attenuation coefficient is described as high as 14 times that of cortical bone. 3 This explains why only a thin layer over granulation tissues is mistaken for bone within the EAC as it is a narrow canal surrounded by bone. Further doubt is created in the context of NOE due to surrounding soft tissue swelling.…”

“…8 Further literature review highlighted a case in which wrongfully, a bony fragment in a supracondylar humeral fracture was reported on plain radiographs in the absence of clinical correlation. 3 Healy et al reported two cases in which silver nitrate was incorrectly identified as a foreign body on plain radiographs of the fingers. 9 A similar case was described by Peter Vu et al, in which the patient unfortunately underwent surgical intervention due to the artefactual appearance of fingertip heterotopic ossification.…”

“…2 Because of its antiseptic and wound healing properties, it is commonly used as a topical agent for cauterizing bleeding points particularly over mucosal surfaces, burning granulations and even cauterizing non-healing ulcers for acceleration of the healing process. 3 Granulations are considered to be one of the diagnostic criteria in necrotizing otitis externa (NOE). 4 These lesions are common and are often managed by direct application of silver nitrate especially after taking biopsies due to use its dual effect.…”

“…1 Silver nitrate not only provides haemostasis but also inhibits fibroblast proliferation resulting in rapid resolution of granulation tissues. 3 The compound appears densely radio-opaque on computerized tomography (CT) imaging mimicking bony fragments and foreign bodies. This is particularly cumbersome when bony erosion is most relevant in diagnosis.…”

The erroneous appearance of silver nitrate on computerised tomography imaging in patients with severe otitis externa; a case series

“…2 Because of these antiseptic and wound healing properties, it is commonly used as a topical agent for cauterising bleeding points; especially over mucosal surfaces, burning granulations and even cauterising the non-healing ulcers for acceleration of the healing process. 3 Granulations in necrotizing otitis externa (OE) are very common and are considered to be one of the diagnostic criteria. 4 These lesions are often managed by applying silver nitrate especially after taking biopsies due to its dual effect.…”