1948 Orr – Somatic pain due to fibrolipomatous nodules simulating uretero-renal disease (“back mice”)

The article is written in an excellent clear narrative. Orr named the back mice as FIBROLIPOMATOUS NODULES.

They presented 5 cases of somatic pain (because of the nodules) simulating uretero-renal visceral disease:

Case 1 simulated a renal colic.

Case 2 simulated a renal colic.

Case 3 simulated urologic or gynecologic ailments.

Case 4 simulated a renal colic.

Case 5 simulated visceral abdominal or gynecological ailment.


Somatic pain due to fibrolipomatous nodules, simulating uretrero-renal disease: a preliminary report

Louis M. Orr (from Orlando, Fla)

PUBLISHED in J. Urol. 1948 Jun; 59 (6): 1061-71.

He was a recognized urologist. He published more than 50 papers.

This work was presented at the annual meeting of the AMERICAN UROLOGICAL ASSOCIATION, Buffalo, N.Y., June 30, 1947.

Lous MacDonald Orr from Florida was a known and recognized urologist that had published more than 50 scientific papers.

Visceral pain vs somatic pain in urological diseases

The clinicians are very aware of the referred pain from the visceral diseases. This is very noticeable in the urological diseases.

But the authors WARN that the clinicians had so long been conditioned to think as VISCERAL PAIN being referred to the EXTERNAL DERMATOMES of the body that they might have become NEGLECTFUL to understand SOMATIC STRUCTURES as being the site of the pain impulses.

They present a NOT UNCOMMON mechanism for the production of symptoms SIMULATING disease of the urinary tract, which are usually OVERLOOKED and had SOMATIC ORIGIN.

Sir Thomas Lewis states that the referred pain was explained by the fact that the viscera didn’t have a detailed representation in the cortex. The impulses from the viscera are represented and referred to the cutaneous segment in default of sharper localization.

From the back to the inferior of the abdomen and the groin

In this paper they deal with the dermatomes D-12, L-1, L-2.

Orr et al. refer to the British investigators Copeman and Ackerman

Copeman and Ackerman dissected the backs of 14 cadavers during the World War II in an effort to determine the legitimacy of complaint in soldiers who presented characteristic symptoms of MYOSITIS or FIBROSITIS of the lower back. They found deposits of FIBROFATTY tissue beneath the superficial fascia in well-defined areas, even in grossly wasted bodies in which most of the body fat elsewhere had disappeared. They called this consistent fat “basic fat pads”. They also observed that the deep fascia had deficiencies through which fat could herniate, also through the neurovascular foramina. They mapped the pain pattern of patients and saw that it correlated with the basic fat pad pattern. It was likewise that the cutaneous branches of the lumbar nerves accompanied by blood vessels pierce the fascia through definitive foramina. Not infrequently were lobules of fat seen partially herniated into these foramina.

Copeman and Ackerman examined soldiers with lumbar fibrositis and found painful nodules that correlated to the “pain pattern” and the “basic fat pattern”. They found the nodules to contain fat and fibrous tissue; they termed them “fibrositic nodules” (also named “back mice”). They couldn’t stain for nerves fibers.

Orr refers to the work of his colleagues: Mathers and Butt that PARTLY disagree with some of Copeman and Ackerman’s statements.

Mathers and Butt have located these “FIBROLIPOMATOUS NODULES” (“back mice”) at numerous points in cervical and dorsal regions along the borders of and over the surface of the erector spinae muscles.

From their studies (not yet published by then) THEY QUESTION the herniation of fat lobules through nerve foramina, THEY BELIEVE that PAINFUL FAT NODULES represent a local pathological process in the normal layer of body fat which lies over the muscles of the back that with a local disturbance can cause PRESSURE upon one or more of the cutaneous nerves (not necessary as an herniated fat).

They prefer the name “fibrolipomatous nodules” rather than “fibrositic”

They focused on the fact that these nodules can be a source of pain in the production of symptoms SIMULATING true ureteral and renal disease. They choose the name “FIBROLIPOMATOUS” rather than “fibrositic” because of the histology of the nodules.

The nodules are PALPABLE to the examining finger, and PRESSURE upon them produces the “pain complained of” and often stimulates distant referred pain.

Diagramatic sketch of a fibrolipomatous nodule ("back mice")

Local injection of novocaine directly INTO the nodule eliminates the pain to the complete satisfaction of the patient.

Surgical removal of the nodule results in permanent relief of pain, local and referred.


They are aware that there necessarily must be and irritating foci affecting the D-12 and L1-L2 dermatomes. The nodules can be “one” of the several causes of irritation.

Previous studies

The work of Ussher in 1933: he described the concept of viscerospinal syndrome. He described that cutaneous, muscular or articular irritation points STIMULATING postganglionic fibers supplying a viscera resulting in SPASM of smooth muscle which, in turn, reflects itself as disturbance in normal physiology of the involved organ. This would be a REVERSAL of the concept that irritating processes in viscera produce reflex spasm of striated muscles which recieve innervation from the same level of the spinal cord. In 1940, he presented large series of cases in which smooth muscle spasm was due to irritation of posterior branches because of articular disturbances. Orr et al. state that “THIS WORK DIDN’T RECIEVE GENERAL RECOGNITION”.

Synaptic connection through the vertebral roots show impulses to the viscus

Orr et al. wondered: Could the nodules disturb the secretion of urine, the function of the ureter and bladder?

Two cases: they had 2 cases that presented frequency of urination that was relieved by removing the nodules (one even was also relieved of bouts of ureteral spasm).

They admitted that they needed further studies, but they presented cases of renal and ureteral pain originating is somatic structures because of FIBROLIPOMATOUS NODULES in patients that were STUDIED REPEATEDLY with negative pathological findings by the usual procedures employed in the diagnosis of urinary tract pathology.


Red blood cells were found in urine

Case 1. 25-year-old man. A man who, while in the armed forces, had a sudden moderately severe pain in the right costovertebral region radiating to the genitalia. There were red blood cells in the urine. The urological examinations were normal. The pain got relieved on rest and worst when driving. Physical examination revealed a tender nodule (“back mice”) at the lateral edge of the right erector spinae at the level of the twelfth dorsal vertebra. Pressure on this nodule produced pain with radiation to the anterior abdomen and right groin. The man stated that the pain elicited by pressure was the same that he felt previously. Injection of novocaine produced COMPLETE temporary relief of the symptoms. Permanent relief was secured by surgical removal. FREQUENCY OF URINATION, which was of minor importance, was relieved.

After 1cc of novocaine injection the patient stated: "my kidney stone is gone"

Case 2. 38-year-old woman. Pain in the left kidney region for 7 years. The pain was dull and constant extending over an area as the figure. During an initial attack seven years before, they made the pressumptive diagnosis of RENAL CALCULUS. All the urological examination showed normal. The patient underwent appendectomy and right oophorectomy without relief. Then they found a PAINFUL TENDER NODULE at the level of the second lumbar vertebra, 3 1/2 cm to the left from the midline. After an injection of 1cc of novocaine the patient said “My kidney stone is gone!”. The pain returned after 3 weeks, and she was advised to have the nodule excised. The following day after operation the patient was free from pain.

Pressure on the nodule ("back mice") reproduced the complained pain.

Case 3. 36-year-old woman. She had pain in the right kidney region. The patient stated that 14 years ago after a twist while riding a horse she had a sudden pain similar to the present moment. The pain was dull, and extended from the right costovertebral angle to the right lower quadrant of the abdomen. There was no dysuria or hematuria. The pain was more severe at sitting. Gentle massage gave temporary relief. The patient was checked by urologist, orthopedist, gynecologist and general practitioners. But during the period of 6 months the pain was unabated. They found a nodule in the L2 region. 4 cm right from midline. Pressure of it reproduced the pain complaint, the injection of novocaine produced complete relief for 5 YEARS.

Pressure on the nodule produced pain referred to the testicle.

Case 4. 27-year-old man. The patient was referred by an urologist for investigation of a PAINFUL nodule in left lumbar region. The pain referred to abdomen and testicle. The patient said that sometimes the pain was like “colicky in nature”. They found a TENDER area in the left side of the back 5 cm from midline between L1 and L2. Pressure on the area referred pain to the testicle. Injection with novocaine relieved the pain completely. The pain disappeared after nodule excision.

The aptient underwent an appendectomy without any pain relief.

Case 5. 34-year-old woman. Pain of 12 years of history. The pain extended from the right costovertebral angle to the lower quadrant. She underwent appendectomy because of the pain without relief. The patient went “desperate” at certain point and was seen by many specialists until they found a “very tender area” in the region of L2, 3 cm from midline. Due to excessive fat in the region, no definite nodule was palpated. Nevertheless, the novocaine injections gave temporary relief for 48 hours and a late surgical removal was done. The surgery revealed a FIBROLIPOMATOUS nodule exceptionally large 3x2x5 cm. The patient remained free of pain for the time being.


They presented clinical cases that showed the “fibrolipomatous nodules” as cause of SOMATIC PAIN that could be confused as of ureteral and renal disease origin because of its dermatoma referral pattern.

They also DEMONSTRATED nerve fibres in the nodules which were NOT previously described (Copeman and Ackerman mentioned in their work the intention to stain, but could NOT do it because of WAR WALFARE).

Except in the very OBESE patients the nodules are usually easily palpable and painful to pressure. Oftentimes pressure would reproduce the distant referred pain.

Published in June 2018 By Marta Cañis Parera    ORCID iD icon

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