Comment tumour growth in experimental animals with considerable interest. Allowing for the usual variations associated with experimental tumours, such as variation in the endpoint tumour weights over the course of the study, there appears to be a significantly greater tumour growth rate in the animals receiving allogeneic infusions of either whole blood, plasma or washed cells in volumes of at least 4 ml in divided doses. This 'dose-response' relationship was also noted by Opelz (1) concerning the influence of allogeneic blood on renal allograft survival, and the similarity with effects in humans and this experimental model is striking. It has been known for some time, however, that the biological behaviour of immunogenic tumours such as the MC sarcomas can be manipulated by rendering the animal immunologically incompetent (2). It would appear that the experimental protocol used in this study has been designed merely to highlight this effect. Allogeneic blood will render the recipient immunosuppressed (maximal after 14 days). The larger infusions are divided into two aliquots 7 days apart, with tumour inoculation 7 days after the second dose. The authors appear to be sensitising the animals with one dose and then reinforcing the immunological insult with the second dose, with tumour passage occurring at a time of maximal immunological 'trauma' within the host rat. The overall effect is enhanced tumour growth. In the authors' own clinical study in human colorectal cancer and blood transfusion, they found that intraoperative blood loss, and intraoperative transfusions were significantly associated with a worse prognosis. Our own figures show that 85% of patients who receive a blood transfusion do so during or within 48 h of surgery, and as few as 13% receive preoperative transfusions only. There is, to date, no experimental evidence to show that allogeneic blood transfusion given at the time of, or after tumour inoculation influences tumour growth rate in a manner described in this study, and raises doubts against direct immunological mechanisms being responsible. If we are to elucidate a mechanism concerning the effect of transfusion on tumour growth in the clinical context, different approaches will have to be considered. Studies such as these, where the endpoints can be manipulated are repetitive and, in general, misleading. RICHARD J LAWRANCE

Surgical Registrar

Southampton General Hospital Southampton, Hants References I Opelz G, Terasaki PI. Improvement of kidney-graft survival with increased numbers of blood transfusions. N EnglJ7 Med 1978;299:799-803. 2 Eccles S, Heckford S, Alexander P. Effects of cyclosporin A on the growth and spontaneous metastasis of syngeneic animal tumours. BrJ7 Cancer 1980;42:252-9.

Optimal operative treatment in acute septic complications of diverticular disease I read with interest the article by Corder and Williams (Annals, March 1990, vol 72, p82). I agree that emergency colonic resection is the treatment of choice in cases complicated by peritonitis. Twenty-two years ago, Roxburgh et al. reported a consecutive series of 25 patients

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with peritonitis secondary to colonic diverticular disease treated by some form of emergency resection, except in one with faecal peritonitis treated by simple exteriorisation (1). Eight patients had primary end-to-end anastomosis (with the addition of a transverse colostomy in one and a caecostomy in another), eight a Paul-Mikulicz excision and eight a Hartmann's procedure. Three patients with faecal peritonitis died and 22 patients with purulent peritonitis survived. There were no leaks in the primary anastomosis cases. Since then, I have operated on many more patients using a one-stage primary anastomosis technique whenever possible (one layer inverting mattress sutures using catgut before the advent of staplers). This procedure is relatively safe as the proximal bowel is not usually oedematous, or dilated, as in cases of acute obstruction. Complications are rare with improved antibiotics and the operation has been facilitated by the use of staplers in the past 14 years. I, personally, avoid the Hartmann's procedure whenever possible, as the second stage, despite the use of staplers, can often be a most tedious and difficult operation, when loops of small bowel are plastered down in the pelvis due to adhesions. R YEO MChir FRCS Consultant Surgeon Royal East Sussex Hospital Hastings, East Sussex

Reference 1 Roxburgh RA, Dawson JL, Yeo R. Emergency resection in treatment of diverticular disease of colon complicated by peritonitis. Br Med J' 1968;3:465-6.

The incidence of congenitaily absent foot pulses This report (Annals, March 1990, vol 72, p99) deals with the incidence of absent pedal pulses in two groups of apparently healthy young persons, aged 9-10 years and 15-30 years, respectively. The authors do not cite any of the published studies on this matter. Immodesty compels me to draw attention to just one of these (1). My colleagues and I not only addressed a similar question by examining 473 lower limbs of persons of both sexes in four age groups from 0 to 79 years, but drew attention to the very great interobserver error that attends the detection of pedal pulses. When there was complete agreement among our three observers the chance of not detecting the posterior tibial pulse in persons under the age of 60 years was vanishingly small (about 0.5%), but the chance that any one of the observers would fail to detect this pulse was some five times greater. We would not have disagreed with the conclusion of Robertson and his colleagues that "an absent pedal pulse... is a significant indicator of peripheral vascular disease", but would have added three caveats. These are that the conclusion should refer specifically to the posterior tibial pulse (which is supported by their own data); that the observer should be skilled in detecting ankle pulses; and that the finding of one observer should be confirmed by at least two others. JOHN LUDBROOK MD ChM DSc FRCS FRACS Professorial Research Fellow The Royal Melbourne Hospital Melbourne, Australia

Reference 1 Ludbrook J, Clarke AM, McKenzie JK. Significance of absent ankle pulse. Br Med J 1962;i: 1724-6.