Renal hematoma is a rare complication of lumbar trigger point block, although it is an important treatment in the pain clinic. We experienced a case in which careful medical re-interview and ultrasonography enabled a definitive diagnosis of acute kidney injury and hematoma caused by lumbar trigger point injection. Among the 276 claims associated with invasive procedures for chronic pain management in the American Society of Anesthesiologists Closed Claims Project [1], 17 involved trigger point injections; however, there are few reports of acute kidney injury or hematoma resulting from lumbar trigger point injections [2]. Serious complications reported after trigger point injection therapy include abscess, necrotizing fasciitis, osteomyelitis, and gas gangrene [3]. Non-infectious complications include pneumothorax [4], which is the most common non-infectious claim according to the American Society of Anesthesiologists Closed Claims Project [1], air embolism, and intrathecal injection presenting as hemiplegia [5].
Regarding the trigger point injection performed by the previous doctor, whether it was done blindly or with ultrasonography-guided technique, how long the needle was, and other detailed information was unknown because it was not reported to us. Therefore, we could not discuss the technique in this case. In the present case, the renal hematoma was a complication of trigger block injection and was not associated with aortic dissection; moreover, the hematoma appeared to be iatrogenic, caused by prolonged bleeding due to antiplatelet therapy. Non-traumatic renal hematoma can be classified into three types: internal, subcapsular, and perirenal [6]. Non-traumatic subcapsular hematoma can also be associated with renal tumors [7]. Hence, it is important to determine the history of a bruise on the abdomen or back and to rule out the presence of a tumor. Most iatrogenic cases occur secondary to extracorporeal shock wave lithotripsy for renal biopsy and renal stones. Secondary infection and hypertension are complications of renal hematoma. In the case of hypertension secondary to kidney injury, termed Page kidney injury, renin hypersecretion occurs in response to the renal hematoma.
Ultrasonography is useful for visualizing free fluid in the trauma setting but is inferior to CT in terms of resolution and ability to accurately characterize renal injury [8, 9]. It is unable to distinguish fresh blood from the extravasated urine and cannot identify vascular pedicle injuries or segmental infarct [7]. However, it can be used for follow-up on hydronephrosis, renal laceration managed non-operatively, and postoperative fluid collection [10]. The lack of ionizing radiation, which is one of the main advantages of ultrasonography, is very relevant for pediatric patients.
In the dorsal subcutaneous to renal anatomy, structures located at a thickness of approximately 3 cm beneath the subcutaneous tissue and fat include the latissimus dorsi, quadratus lumborum, and transverse abdominal muscles; the inferior surface of the diaphragm above the kidney; and Gerota’s fascia [11]. Between the transverse abdominal muscles and Gerota’s fascia are perirenal fatty tissues located inferiorly and laterally to the kidney. The kidneys are located between the 11th thoracic and 3rd lumbar vertebrae, with the left kidney higher than the right kidney. In addition, the lower pole of the kidney is located close to the skin, and for this reason, it is chosen as the site of needle puncture for the collection of renal biopsy tissue. In the present case, trigger block puncture was performed at the level of the left first lumbar vertebra. Because of its vulnerability to injury of the lower renal pole, great care must be taken when performing skin puncture in this area. Although the dorsal kidney does not contain large blood vessels, the kidneys have rich blood flow. To minimize the risk of kidney injury, and on the basis of the present case, it is considered that the only recommendation is to carefully perform trigger point block to prevent renal injury in patients receiving aspirin.
The present treatment strategy was conservative and included follow-up observation because renal capsular hematoma is sometimes accompanied by bleeding. Our careful re-interview and primary ultrasonography enabled accurate identification of the cause of bleeding in this patient and guided the course of appropriate treatment.
In conclusion, hematoma caused by lumbar trigger point injection is a relatively rare condition. Our case report highlights the importance of careful medical re-interview and ultrasonography at the primary medical examination.
