LETTERS TO THE EDITOR Ann. SLrg.- January 19 90 June 27, 1975 that a reversed portal flow would result in a negative HA:PV ratio and nowhere in the report one can find any Dear Editor: reference to negative ratios. The article entitled "A Review of Echinococcal DisAlthough our paper did not deal with any attempt to ease," Lewis, Koss, and Kerstein in the April, 1975 correlate the HA:PV ratio of flows with the so called Annals by makes "maximum perfusion pressure," Smith's reference to it ease which can many excellent points concerning a dispose extremely complicated problems in in his letter opens the door for some discussion of the treatment. subject. In the first place, it is frought with dangers to The French literature presents an enormous experiperform a regression analysis on the basis of the mean ence with Echinococcosis and some points of view there values of any variable grouped according to arbitrary concerning hepatic forms of the disease merit emphasis. cut-off limits. Then, it is difficult to conceive any Most surgeons protect the abdominal contents with physiological or pathological reason that would justify a pads saturated with two percent formalin. A distinction correlation between the ratio HA:PV and the "maximum must be made between simple and complicated cysts. perfusion pressure." We have measured this ratio in 41 The simple, young cyst containing clear fluid can be patients with cirrhosis and portal hypertension' and treated by simple removal of the hydatid membrane; it is found a wide spread of its value ranging from 0.23 to 4.71 rarely necessary to treat the remaining soft-walled cavity with a mean value of 1.13 + 1.01 S.D. What is more further.2 The older, multivesicular parasite has a thick, important, in 22 of these patients we had also the value of often calcified partially second wall of compressed hepathe "maximum perfusion pressure" and we found a comtic tissue. These are the cysts frequently complicated by plete lack of correlation (r = -0.12) between this presinto the bile ducts. Their treatment of choice is openings sure and the ratio HA:PV (see Fig. 10 in our reference 1). which cystectomy, may entail anatomic hepatectomy.1 Not having the raw data in the studies by Smith we can Arteriography and cavography best used to assess the only speculate that his correlations may have been biased vascular risk of this sometimes are hazardous undertaking. If by the bracketing of his patients in small groups. He gives cystectomy is impossible or judged too dangerous, partial a plausible example of this possible bias in his letter while resection with drainage is accomplished.4 Biliary orifices stating that in Stage III he had values of HA:PV in only are sought and sutured. In complicated cysts we feel three patients. If one subtracts one degree of freedom T-tube drainage of the main bile duct is mandatory since used in the determination of the mean, the value of the bile leakage and/or infection are otherwise almost inevitlatter and of its standard deviation becomes highly ques- able.3 tionable. The problem is aggravated by the fact that one Marvin B. Corlette, M.D. of these three patients, the one with reversed flow, must 19 Muzzey Street have had a negative HA:PV ratio. Mass. 02173 Lexington, Finally, the association of a negative "maximum perfusion pressure" with his case of reversed portal flow References should not imply a cause-effect relationship. In a previ1. Bourgeon, R., Catalano, H. and Guntz, M.M: La Perikystectomie ous paper2 we have shown that the splanchnic and hepadans le Traitement das Kystes Hydatiques du Foie. J. Chir., 81, tic occluded portal pressures used in the construction of No. 2, 153-174, 1961. the "maximum perfusion pressure" are unrelated to the 2. Demirleau, J. and Noureddine, M.: Le Choix de l'Operation dans les

magnitude and direction of the portal flow. With the portal vein occluded by a clamp, the hepatic and splanchnic occluded portal pressures are determined uniquely by the ratio of the outflow to the total resistance in the hepatic artery-hepatic vein and in the splachnic-collateral parallel circuits.

Kystes Hydatiques du Foie. Mem. Acad. Chir., 90:12:69, 1964. 3. Mendes, A.C. and Bismuth, H.: Problemes Actuels dans le Traitement des Kystes Hydatiques du Foie. Journees de Chir. Hepato-Biliare, H6pital Paul Brousse, May, 1975. 4. Rives, J.: A Propos du Traitement des Kystes Compliques du Foie. Interet des Methodes Combinees. Mem. Acad. Chir., 90, No. 4-7, 140-145, 1964.

Augusto H. Moreno, M.D. Dear Editor: St. Vincent's Hospital and Medical Center of New York Dr. Corlette had recently written to us, and it is clear New York, New York 1001 1 that he indeed has had an extensive experience with this problem while working in France. We do not recommend References the use of Formalin even on pads protecting the abdomi1. Burchell, A.R., Moreno, A.H., Panke, W.F. and Nealon, T.F. Jr. Hemodynamic Variables and Prognosis after Portacaval Shunts. nal contents because although some authors feel that Surg. Gynecol. Obstet., 138:359-369, 1974. one-half to one per cent Formalin is safe, most are agreed 2. Moreno, A.H., Burchell, A.R., Reddy, R.V., et al.: The on the fact that greater concentrations are probably unHemodynamics of Portal Hypertension Revisited: Determinants and Significance of Occluded Portal Pressures. Surgery, 77:167- safe and that even on pads which are protecting the 179, 1975. abdominal contents, enough can be absorbed which may