Lung Ultrasound (Fungal Pneumonia) Case Study
Internal Medicine Blog: Vet BLUE Lung Ultrasound Case Study – Fungal Pneumonia
“Misty” is a 4 year old F/S English Setter who presented to her veterinarian for inappetence and weight loss. She had lost 6 lbs in the course of 3 weeks. She had an occasional dry cough but no other specific clinical signs were reported. The working diagnosis based on a brief ultrasound exam by the referring veterinarian was stump pyometra.
A complete abdominal ultrasound was submitted for review. The exam did not show any specific abnormalities to explain her clinical signs and a stump pyometra was not evident. Thoracic radiographs were recommended for additional evaluation. Her referring veterinarian was reluctant to perform radiographs because it was felt that the cough was insignificant based on clinical impression and unremarkable lung auscultation. However, the referring veterinarian was persuaded to allow me to assist with a Vet BLUE lung ultrasound exam (part of the Global FAST protocol).
Fig. 1: Shred sign seen with focal lung consolidation. In this case, the shred sign is due to fungal pneumonia but it may be seen with other alveolar diseases including bacterial pneumonia, hemorrhage or severe pulmonary edema.
Fig. 2: Nodule sign due to fungal pneumonia. Nodules may also be seen with neoplasia
Fig. 3: Nodule sign. Note the bright acoustic enhancement in the far field of the nodule. This can be seen in the adjacent images.
Interestingly, the Vet BLUE lung ultrasound exam was performed in less than 5 minutes. There was no evidence of interstitial edema (absence of B lines or rather dry fields at all 8 Vet BLUE regional sites). However, multiple focal nodules were evident in the following lung lobe regions: Left cranial lung lobe region- nodule (5.2 mm), right caudal lung lobe region- (3.3 mm); right perihilar region- nodule (7.2 mm); right middle lung lobe region- shred (6.5 mm). The findings suggested multifocal nodular disease and thoracic radiographs were now indicated.
Fig. 4: Thoracic radiographs showing hilar lymphadenopathy and patchy interstitial pattern in caudal lung fields. No nodules were evident on VD thoracic radiographs.
Given the dog’s age and travel history, fungal disease was considered most likely; however, neoplasia could not be entirely ruled out. Thoracic radiographs were subsequently performed and showed hilar lymphadenopathy and patchy interstitial pattern (non-definitive). Based on these findings, fungal titers were submitted and diagnostic for Coccidioidomycosis. Itraconazole was started within 48 hours.
The take home message of this week’s blog is that lung ultrasound is a rapid lung screening test that may be more sensitive than lung auscultation and thoracic radiography for peripheral lung pathology (this is well documented in the human literature). I have found Vet BLUE invaluable in my internal medicine practice. It is not uncommon to find evidence of lung pathology when imaging caudal lung fields through diaphragm on hepatic view with cases presented for abdominal ultrasound.
The basic 5 lung ultrasound findings are easily teachable and include: dry lung (lung slide and A-lines), wet lung (B lines), shred sign, tissue sign and nodule sign. Using the Vet BLUE pattern-based approach, more evidence-based lung information is provided over routine means of lung auscultation and thoracic radiography.
Assumptions are made in using lung ultrasound and a big assumption is that acute conditions including pulmonary edema and inflammatory conditions such as pneumonia make it to the lung periphery. This is an important potential weakness of lung ultrasound since unless the disease or condition makes it to the very outer lung, it will not be visible sonographically. Therefore, lung ultrasound cannot replace thoracic radiography and should be used in conjunction with radiographs. However, it has been shown in human medicine that most acute conditions do in fact make it to the lung periphery and lung ultrasound is an effective means of diagnosing and recognizing lung pathology otherwise missed by lung auscultation and routine radiography (including pulmonary edema and pneumonia).
The bottom line in this case is that this patient would have been sent out the door without the correct diagnosis (or its suspicion) or with a course of ineffective antibiotics. It is possible (and likely) that the dog may not have returned until the disease was significantly more advanced and she was showing more significant respiratory signs including respiratory distress.
The use of Vet BLUE lung ultrasound has been invaluable in my internal medicine practice. In this case, Vet BLUE helped the referring veterinarian capture the case when treatment would be more effective rather than waiting until the patient presented with advanced disease, snowstorm lungs, and in respiratory distress.