Part of the differential diagnosis for both acute and chronic flank pain includes the nearly forgotten condition of ‘12th rib syndrome.’ This has also been described as a form of intercostal neuralgia and is often be overlooked by the urological surgeon, especially in an age where spiral CT has almost replaced a thorough clinical examination for patients with flank pain. A history of stone formation or indeed a confirmed urinary tract calculus should not distract the examining clinician from considering ‘12th rib syndrome’ as a possible diagnosis. Confirmation is made by careful clinical examination, elicited by exactly reproducing the patient’s pain on point compression over the tip of the involved rib, usually the 12th or 11th or at the 10th costchondral junction.
The ‘hooking manoeuvre’ is a simple clinical test described in 1977 , in which the examining clinician places his or her hand underneath the lower costal margin and pulls anteriorly. This action often elicits agonising pain and the authors have known patients to collapse as if struck down with renal colic.
Frequently encountered and well documented as a cause of anterior upper quadrant pain, this condition has also been described as ‘floating’ or ‘slipped-rib syndrome’, or traumatic intercostal neuritis.
Published reports appeared in the early 20th century but since then little has been written on this subject in English-language journals and the condition is rarely discussed. The symptom complex was first reported in 1919  as a cause of pain that ‘may simulate the referred pains of visceral disease’ and later descriptive reports further characterized the condition [3–5]. These early papers eloquently describe the complaint, but perhaps more importantly, allude to the need for astute clinical examination to avoid unnecessary investigation and misdiagnosis.
Most published reports in the 20th century were anecdotal or descriptive case series, but two authors reported this condition in 1–5% of patients attending general medical or gastro-enterological clinics [6,7].
Bilateral cases have been reported but the condition is almost always unilateral, with pain localized to the tip of the 10th, 11th or 12th rib, which might be exacerbated by movement. The quality, severity, location and distribution of the pain should be established by a careful history-taking, together with the variability, which relates to the ‘response to circumstances which move or otherwise irritate its source ’.
The pathophysiology is thought to involve a loosening of the costo-chondral cartilages of the lower ribs, notably the eighth, ninth and 10th. Respiration then causes the deformed end of the affected rib to slip or rub against the inside of the adjacent superior rib tip, which can result in severe pain. Alternatively, the condition can be due to inflammation of the tendinous insertions into the rib tips, similar to the pathophysiology of chronic ‘tennis elbow’.
The aetiology is unclear and has been attributed to both direct and indirect trauma, such as sudden extension, flexion or twisting of the thoraco-lumbar junction. As cited by the original descriptions, the close association of the intercostal nerves and the sympathetic system accounts for the symptoms that can exactly mimic intra-abdominal pathology.