Key words: lumbar plexus block, renal subcapsular hematoma, complication.
THE lumbar plexus, which branches to the genitofemoral, lateral femoral cutaneous, obturator, femoral, and lumbosacral nerves, is located between the quadratus lumborum and psoas major muscles (a part of the plexus is contained within the psoas major muscle). Lumbar plexus block (LPB) has been described for use in patients with lumbosacral and lower extremity pain. [1-4]Psoas compartment block is one form of LPB. .
Because the lumbar plexus is adjacent to the retroperitoneum and peritoneal cavity, introduction of a block needle into adjacent structures, such as the kidney, may result in complications. In the method described by Chayen et al., an approach for LPB at the level of L4 vertebral body was presented. However, some practitioners introduce the block needle at the L3 level, at which there is a probability that the needle tip will be introduced into the kidney (Figure 1). We present two cases of renal subcapsular hematoma subsequent to LPB at the L3 level.
A 71-yr-old, 47-kg, 155-cm woman received right LPB for treatment of low back pain associated with a herniated lumbar disc L3-L4 and L4-L5. The block was performed four times for 4 weeks at the level of L3 using a loss-of-resistance method, with a 15-cm 20-G needle and 10 ml 1% lidocaine. However, the low back pain became more intense 1 day after the last LPB, and she had difficulty walking for several days. Pain was localized to the right low back, but sciatica did not increase. The pain was treated with 750 mg oral mephenamic acid. Microscopic hematuria and slight elevation of the C-reactive protein concentration were noted, although other laboratory parameters were within normal limits (Table 1). She was instructed to rest quietly at home. The pain did not decrease 10 days after the block, and ultrasonography (Figure 2) and computed tomography (CT; Figure 3) examinations revealed an abnormal mass on the surface of the kidney. The renal capsule was intact and the mass was retained within the capsule. No signs of associated infection or nerve injury, such as increased body temperature, abnormal tendon reflex, muscle weakness, or paralysis, were noted. A CT image of the mass was amorphous and showed intermediate density between those of water and kidney parenchyma. The image density clearly differed from that of renal cyst, injected local anesthetic, or renal tumor. The patient exhibited no abnormalities of hemocoagulation (Table 1). From these results, the diagnosis was renal subcapsular hematoma due to renal injury by the block needle after LPB (Figure 1).
The patient was instructed to rest for an additional week. Microscopic hematuria was resolved 2 weeks after LPB. By 3 weeks after the last LPB, localized low back pain due to the block had resolved. Four months after the block, the hematoma was reabsorbed spontaneously, and neither abnormal signs and symptoms nor aberrant ultrasonographic (Figure 2) and CT (Figure 3) results remained.
A 68-yr-old, 44-kg, 155-cm woman had severe low back pain due to spinal spondylosis. She received left LPB at the L3 level using the loss-of-resistance method, with a 15-cm 20-G needle and 10 ml 1% lidocaine. Low back pain became more intense 1 day after LPB. The pain was localized in the left low back, and no root signs were noted. The pain was treated with 200 mg intravenous diclofenac. However, the pain remained severe, and the patient could not walk for several days. At this time, microscopic hematuria and slight elevation of C-reactive protein and lactic dehydrogenase were noted, but other laboratory parameters were within normal limits (Table 1).
On admission 3 days after the block, ultrasonography (Figure 2) and CT (Figure 3) revealed an abnormal mass compressing the kidney. Features of the mass and signs and symptoms were the same as in case 1. Coagulation was normal (Table 1). From these findings, renal subcapsular hematoma due to renal injury by the block needle after LPB was diagnosed.
The patient was instructed to rest quietly for 1 week. Microscopic hematuria disappeared 1 week after LPB, and the pain had markedly decreased 2 weeks after the block. After 10 days of hospitalization, she was discharged. Six weeks after the block, pain due to the procedure had disappeared completely. The hematoma reabsorbed spontaneously, and no abnormal signs and symptoms or unusual ultrasonographic (Figure 2) and CT (Figure 3) features were noted for 4 months after LPB.
Because the lumbar plexus is adjacent to the kidney (Figure 1and Figure 3), there is a risk of injuring the kidney during LPB. In patients with nephroptosis and the thin muscles, renal injury during the block is considered to occur more easily (Figure 1). Both of our patients had nephroptosis (demonstrated by x-ray photographs with the patients standing) and the thin muscles (Figure 3). Thus, the block needle should be introduced at L4 or L5 for LPB.
Pain due to renal subcapsular hematoma is considered to be caused by stretching of the renal capsule, and pain intensity may depend on the size of the hematoma. When the hematoma is small, pain may not be present.
Percutaneous needle biopsy of the kidney is accompanied by microscopic (rarely visible) hematuria and a few serious complications due to hemorrhage. [5-8]Renal injury by a block needle may be similar to that produced by biopsy. For renal subcapsular hematoma after LPB, observation and care, similar to that after biopsy (Bed rest for at least 1 week is recommended. ) is necessary to prevent repeated hemorrhage due to elevation of blood pressure.
Bed rest for 1 week would be appropriate from the perspective of severe pain management. Nonsteroidal antiinflammatory drugs, such as mephenamic acid and diclofenac, were given to our patients but were not effective. Other forms of pain management, including treatment with analgesics and continuous epidural block, might be considered. Eventually, the hematoma in each patient was reabsorbed spontaneously, and no further treatment was necessary.
To avoid renal injury after LPB, several precautions might be considered: (1) the block needle must be introduced at the level of L4 or L5, (2) the location (depth and laterality) must be visualized by encountering the fourth or fifth lumbar transverse process, [1,2](3) confirmation of the nerves by electrical stimulation is helpful, and (4) performing block procedures under x-ray fluoroscopy may be desirable. These procedures may be appropriate for other nerve blocks, such as lumbar sympathetic ganglion block, LPB, and celiac ganglion block, to avoid renal injury.